I also always return the favor by having my kids' friends sleep over with us. It also serves to build a network of other helpful, understanding parents. Now there are a few of us who help each other when anybody needs it driving to practices, if somebody is running late for school pickup, emergencies, whatever. I would never dream of asking my coparent (counterparent) for help with anything - he sees stuff like that as an opportunity to make my life harder and gets great satisfaction from it.