There's always the sweet spot, but like almost everything involved with predicting the future you rarely know what that is. So you take an educated guess and do what feels right, and the people you know and the media you consume paint that normal for you. Hopefully you don't have a warped perception, because you won't know under after the damage is done.
I think the main issue is parents are largely ignorant of what’s important for a new generation - especially when things are undergoing radical technical change.
My fiancée is reading Walden - and there are comical similarities to a modern day van life Silicon Valley programmer. The industrial revolution left parents at the time clueless - something similar is happening again.