... I never went further than hiring them, thanks for pointing that out.
I usually do science mode, as I'm not really a fan of the contracts/money supply, but full sandbox is boring because none of the experiments have any purpose there. Along with that, I like having to level up my kerbals, it gives something minor back for me to do without being too tedious (IMO), and gives a bit more focus in the early stages of a save (or when gearing up for kolonys).