WLB as an associate at HF and trajectory thereafter - how easy is it to start a family / spend time with family outside of work?

I think the real question I have is how easy is it to wind down and spend real quality time with family (or friends, but without getting completely smashed in order to turn your brain off)? Starting at MM end of August and biggest issue in PE right now for me is turning my brain off after work (and thinking about various)

I'm 26 and want to get married in 2 years and have kids in 4-5 years.

want to work 10-15 years at minimum i'd say (guessing that budgets about 3 blow-ups which i'll take as they come) assuming i get promoted to the analyst and have to find different shops a couple of times, and maybe one day PM but thats more of a fingers-crossed scenario. 

also length of average career? what are some ways people keep themselves occupied after leaving the space? dont think i'd switch strategies