BitTorrent clients keep track of your upload/download ratio (seed/leech), and your priority on torrents will go down as your ratio goes down. If you are getting the "dot-torrent" file from a private tracker, that web site will tell you the rules about required seeding times or ratios. Usually on those sites, your ratio and "hit-n-run" stats are available to everyone there. 5 or 6 hours is not much time, usually 24 hours is a minimum on those private trackers.
For public sites there is usually no rule, just etiquette that you will seed back for the sake of the "swarm." You won't be hunted down, but your download speeds will suffer.
Different torrents are different regarding seeders and leechers over time. For instance, if an open source software publisher puts out a huge daily bug fix, the torrent will not seed back after the tomorrow's is put out (no one wants it anymore), but if you download something when it's fresh (last night's Ween concert, for example), and if it's good, then there may be big ratio-building opportunity for weeks of productive seeding.
The threat of your IP address being a target is real, when it comes to the governments and copyright holders tracking you down (IF you were downloading something you don't have rights to), but not in the torrent communities themselves. The torrent trackers might ban you from their site, but that's about all. You should read some articles on the BitTorrent protocol (see references for two).