Well, I have 7 tanks (6 male and 1 female). I usually will clean 2-3 tanks one day then the next 4 the following day. I have four 2.5 gallon tanks, two 2 gallon tanks and one 1 gallon tank (temporary). I spend a good amount of time watching my guys, as three are on my dresser, and three are on my desk. I feel bad for my 7th (Big Red), as he is in my sister's room and just doesn't get much attention. I call him mine, but he's mostly hers though she doesn't care for him at all. I think I might see if she'll let me move him to the Rec room where he'll get more attention.
Eventually, once I have a place of my own, I'm going to get a larger tank or two and split them. That way I have one heater and one filter for each tank. It does get pricey making sure each tank has a heater and filter!
For whatever reason my parents let me have as many betta tanks as I want, but won't let me get larger tanks.
So, I just maintain what I have knowing that one day the work will be less! hehe