ExH and I stick to the schedule, even if one of us has to travel. The traveler has to find a way to take care of the kids. If that way ends up being the other parent, fine. But there are no swapping of days. If we don't see the kid for a week because of travel or vacation or such, so be it.

DH and BM regularly worry about "time with the skids" and swapping schedules and BM makes sure she's never short on days. Both of them have professed how hard it is to go without the skids for more than their regular duration.

DH and BM also are more daddy and mommy than parent.
ExH and I are definitely more parent than daddy and mommy.

It's that difference in attitudes that I think makes the huge difference. It's why DH "runs out" of parenting and is frustrated by having to parent...it doesn't fit the paradigm or his schedule of when he has time to parent. Seems to be the same for BM. Her babies need mommy more than a parent. And they both miss the skies soooo much.

I know ExH and I like the break that comes when my kid is at the other house. You can refuel and get things done so you can be ready to parent again. Parenting is all-the-time and the break is helpful so we don't mess with it.

I know this meandered so if someone else can say it more concisely, please help.