One of the biggest problems of torrenting is that there's often older files out there that are 97%+ complete but missing a small part, with a bunch of people all stuck at the same amount. Hopefully a person with the complete file eventually comes back online, but until then everyone is screwed.
Why not have a "cold storage" type of system, so that you don't have to completely remove it to get it off your list? I'd much rather have thousands of old torrents online with limited access to help fill problem spots, but not have to deal with thousands of stopped, offline files in my list that I have to put online from time to time.
It's probably way too much work for you to care about, but I think it's something that would really help the whole system overall if more older "offline" files were available.
I read a while back that the average life of a torrent is less than 40 days.
I would assume that most of the use of torrents is to facilitate instant gratification, seeking the latest prolefeed. Propogating new releases of Free Liberated Open Source Software also benefits greatly from torrents but I believe that is a small part of the traffic and such releases also get stale very quickly.
I typically leave torrents that are more meaningful running, patiently waiting for the return of the seed. And sometimes it does happen. Once I saw it took over 3 years for a torrent I wanted to complete.
Perhaps a better system would be to have the library locked in, even if it is in micro-seeding state. Obviously the content is still out there, on someones computer, but there is no current ability to communicate with the seeds for orphaned torrents.