staying overnight at a play partners place... too far?

we've had the same play couple for about a year, weekly-ish, always at theirs or ours, always finishes around midnight, we go home, debrief in the car, sleep at home. they've invited us to stay over a couple of times and we've always made an excuse. theres something about waking up there, having breakfast together, the morning after intimacy thing that feels like its crossing into something else. is overnight a normal next step or is it more loaded than people admit? we love them, but theres a part of me thats worried that stayng changes the friendship dynamic