This. my bots are task based and do 11 different skills (all f2p), and can do 10 quests.
They can last anywhere from 4 hours to 72 hours of active online time.
Currently being a normal member, I can only run 1 bot at a time. (code is already there for multiple servers, and as many bots as I want). So giving a good estimate isn't really something I can do.
But skills that REALLY set off the ban hammer are woodcutting, mining, and killing chickens. I just recently added runecrafting, so we'll see how that is.
But the bot has to get Rune Mysteries done, mine essence, buy an air tiara from the GE and then it can RC. It might be awhile running 1 bot at a time.