I agree this is a separate ticket from #1408 but don't see a lot of demand for this feature.
Please reconsider, because I've wanted this feature for years. There are many sites that require seeing for a minimum amount of time. I'm constantly forgetting about this rule, because I download from different sites, and I occasionally remove torrents before the time limit. If I could say "seed to a ratio of 1.10 OR 30 hours" I would be set.
Given the alleged code modification wouldn't be that hard (according to comments in #3779), what's the harm in offering this feature?