That's one of those questions, really impossible to answer as each seller is different. Things like a work/life balance come down to the individual themselves, then things like sales come down to the types of products and how competitive those products are in regards to orders. So unfortunately, everyone is going to be different.
I would suggest the very successful dropshippers put quite a lot of time into it because it's a very research heavy market to work in. You can't just find a few products and sit back, you have to be constantly researching the market, watching what your competitors are doing to make sure you stay out in front of them or you can see sales disappear over night.
The easiest way to put it, it's like most things. the more you put into it, the more chances you have of getting more out of it :)