I handle every day that I can, considering I only have one ball python thats not a whole lot of handling a week. I feed on Sundays and I like to not handle on feeding day as it may stress her out. I also never handle Monday or Tuesdays, I tend to wait until Wednesday to handle her. So Wednesdays to Saturdays tend to be my favorite days of the week.

My room is not that cold and I set up a sheet on top of my bed for her to explore. I have some extra half-logs and branches (all disinfected) that I sometimes take out and put on the bed and she "loves" playing with them. She's in a 20 gal right now, so she doesnt get the opportunity to roam around on natural environments (wood), because all I can fit is two hides and a water dish. I try to only handle for 15 minutes at a time, but sometimes I get carried away and its probably around half an hour at the most.

I havent seen her ball up since the first week I've gotten her, and especially not when i handle her, and I agree with everyone else who posted. As long as your ball is eating regularly, you can gauge how much handling is OK.