I have 5 BP's and handle them about twice a week (holding my Spider right now:) ). The amount of time depends on their personality; one is held for just a few minutes to get some exercise outside the cage because handling really stresses her out (but she's getting A LOT better in recent weeks), two are held for 15 minutes, and the others maybe around 15-30 minutes because they are my educational show animals and are really relaxed and laid back.
Unfortunately with work and a full-time schedule at school (vet tech major) I've been holding them less than that. Plus, I'm planning on getting at least 8 more next year (saving money is slow going right now lol) so it's unlikely I'd be able to handle all of them on a weekly basis.