I know you want all your uploads available all the time.
As long as they have been seeded to completion, you can let them slip into "archived" status. You can stop seeding them and either start them when you see leechers or have extra bandwith.
You could further leave them until someone hit's the "seed needed" button if you like.
It's nice to seed all the time, but sometimes you just can't.
As long as you are "willing" to seed when you get a request, there is no need to seed 24/7 if your bandwith is an issue.
