There are some preservation efforts on a couple of the big movie trackers. One is "donate Xtb of space and use this script to manage it" so you don't choose the torrents, they get assigned till your donated space is full.

In Another gives bonuses for adopting torrents where the original seeder doesn't want to/can't seed anymore.

Neither are perfect but as one of those 1 in 1000 its nice to help where I can.