i try to do as much as possible, but depends on weather really as i have no menage, try to keep them to about 30 mintes but depends on horses frame of mind!
I school normally 4/5 days a wk in the winter, do BD on Wkend's and he has one relaxing day (either hack/lunge). I school between 30 mins - 1 hr depending on how he is going. If he's going very well and has worked hard then I reduce the time. When I school in the double he works much harder so tires out a little quicker so I try not to push him past 30 mins.
I school out on hacks as well as in the school. I get them in the school about 3-4 times a week and they get schooled form between 30 mins - 1 hour depending on how cooperative they're being.
I school in the areana as well as on hacks etc. At the moment my legs are not strong enough to ride Ru as he is used to so i school untill my legs go to jello, I always end on a positive and can vary from 20 mins to 60 mins. Lunge, long rein, pessoa as well.
Daughter schools her pony a couple of times a week, either flat work or jumping and hacks, hunts and competes most other days. Usually ridng 5 or 6 days a week. She also schools my horse about once a week if she has time as I hate schooling!