When I first started downloading, I thought uploading would get me in trouble, so I would cut the torrent after I saw it completed.
I don't hit and run any more. I've gone as far as redownloading files off of usenet just to seed to get out of the pink on FTN for torrents that were over a year old and probably only a few hours shy of the informal requirements. There was a streak back then that I was having HD problems and files kept getting corrupted and my Mac was bugging out so I had to reinstall every couple of days. FUBAR'ed HD that had to be replaced (got a new PC anyway).