I can tell you from my experience as both a stepmother and a biological mother.

My DH and I moved with the kids. My husband works for the Federal Government. We move about every three years. My ex tried to stop us from moving the kids. The judge dismissed the case and allowed us to move.

We have custody of my stepkids as well. At one point we lived about five hours from their mother. We moved across the country. She tried to stop us from moving the kids. And the judge let us move with them.

Not saying you'll have a similar experience. But we have never had a problem moving with the children. Bottom line. We provide 100% of their financial support. We weren't moving to be spiteful. And every move meant a very substantial pay increase which directly benefited the kids.

I will say that had my ex or my husband's ex been more involved with the kids on a day-to-day basis, we might have had more trouble. BM only saw the kids a couple of times a year when we lived closer. My ex might have seen our kids once a month. That made a huge difference.

We did deal with the BM wanting to relocate out of state. It was becuase she couldnt find work but had someting lined up out there. I told BF to agree but to his terms. He actually would only agree if:

1)She lowered the outrageous CS to something more resonable

2)She split ALL travel cost no matter what (we really should have had her pay it all in hind sight)

3)We wanted ALL summer, every spring break and a week at christmas alternating christmases each each (again hindsight I would have gone for both weeks cause she wouldndt even give us an extra day)

My sister petitioned to leave the state from her BD. They tried to stop her but in the end the court will make you guys agree. I would just make sure its on your terms and get everything in writting.

SHE pays for ALL travel costs
You need to get as much time as you can
I would also set up the agreements when it comes to phone calls and such cause there have been issues with that too.

Good Luck!

BM in our case just up and moved SDs out of state when they were 7 & 8. We tried to fight it in court but the judge was very pro BM and our attorney at the time was not very aggressive. After BM lied to the judge multiple times, he still gave her permission to keep the kids out of state. It really ruined my DH's relationship with his daughters so much so that they no longer speak (SDs are 18 & 19 now). BM is the queen of PAS. All BM wanted was an ATM so that she could raise the kids however she felt fit at the moment. Both kids dropped out of high school (or got kicked out, we never found out which). BM also had an older daughter who dropped out of high school....great track record huh? Our daughter is graduating this year with honors. Our son, is in special needs class, but will graduate and is not a dicipline problem to the teachers. We aren't perfect but sure could have done alot better with the SDs if they would have lived here. I firmly believe that judges really need to start taking responsiblity for the mistakes they make.

We live about 5-6 hours away from SS and it's been that way since my husband told her that he wanted a divorce. She never got permission from anyone (my husband or the court) to actually move out of the county, however, my husband felt:
A) Guilty for wanting to divorce her -- even though he had been telling her he wanted out for years and she never took him serious and he never followed through those times.
BM's mother lives where she moved and, at the time, he felt that it would be best for everyone if he didn't try to force her to stay here.

That is why she was able to leave and, of course, this was a big mistake as DH came to realize. The night he told her he wanted the divorce and wasn't going to change his mind, She tried to take off his clothes and started kissing on him, but when he stopped her and told her once again that there was no chance in hell he was staying with her, she started screaming at him to get out and went ballistic throwing a bunch of heavy large objects (including a very expensive crystal Swarovski ball that DH's mother gave him) through the wall. He had to go upstairs and quickly wake up his (now ours, as I have adopted them) 2 girls, then say goodbye to SS, who was 6 at the time, and drive to his parents home 7 hours away in the middle of the night. It was Summer time, so he planned to drop the girls off at his folks for a little while to visit while he dealt with her immediate wrath.

However, when he got back in town and told her he was coming back to get some things and go to a hotel, she informed him that neither he, nor the girls (then 7 and 12) were welcome back in the house and she changed the locks and disabled the garage doors so he could not access it. She told him that his and the girls' clothes would be packed up and put outside for him to pick up. When he got there, he saw all of their (the girls' included) clothing and personal effects in trash bags or nothing at all strewn all over the front yard. She then informed him that she was moving and that she would leave a key with someone for him to pick up once she and SS were gone. He called a lawyer at that point (one of the worst lawyers in history if you ask me, and someone we later replaced) who informed him to just stay away from the property until she had gone. Thank God he had and has the financial means to have done that.

Well, finally she called him and told him that she would "allow" him to say goodbye to SS before they left with her mother. When he got back into the house finally (which was a whole other fiasco!), he found that she had emptied the entire place (3500 sq. ft!) and had taken EVERYTHING except the kitchen sink... literally! She even took the refrigerator! She left the girls' beds but took their electronics and pretty much anything of value. She even took the silver frames off the pictures of my DH's cousin who had recently passed away tragically and threw the pictures out on the floor. It was like the Grinch had stolen Christmas again!

Make sure there is a SOLID court order in regards to visitation, otherwise, you could find yourself in our situation. There is so much more crap than just what I have written above, but that's another story all together! Good luck!

Also, we have to pay 100% of SS's travel costs and, get this, BM refused yet again to send him this last time because there was a newly imposed $25 UM fee each way that you can't pay online. It has to be paid at the ticket counter which we told her we would reimburse her. Instead, she decided to wait until she got to the ticket counter and act like she didn't know about the fee and refuse to pay it. She refused to put him on the plane and then waited to inform us of it until we were at the airport and didn't see him get off the plane. We now have to send her a $25 "gift card" a week prior to his scheduled visit to pay the fee since we are technically supposed to pay for travel costs. Of course, she still doesn't send him. We had an idiot lawyer the first time around, which is why we got this stupid deal to begin with, now we have a kick ass lawyer but really expensive.

BM moved without notice when SD was 5yo out of state, 4-5 hours away. She was given the choice by the judge to provide all transportation for every weekend visitation plus all summer and holidays or move back. She moved back. 5 years later she gave up custody and moved to the same state but now 8 hours away.