I also work full time, 9-5 mon-fri. A good plan for me is to do 1 test split up throughout the weekday evenings, and one on the weekend. That way you get a bit of a break and you're only doing and hour or 2 in the evenings. I try to work until my focus really goes and not to push it, once my brain checks out then I'm just wasting time. Even if you only get 1.5 tests done that week, it's still helping.