I... what? I don't follow your logic here.
If you play more, you get more Seed drops. In 16 hours you can do around 50 Experts if you're really anal about BP ticks in a day, without Seeding. 50 Experts will probably drop you 25+ Seeds. That's a gain of 200+ Seeds per Union event, without even counting the rewards or the daily big Seed.
Meanwhile, if somebody can only play around eight hours a day, then the gain is about half of that.Only if it takes you 20+ minutes to kill one. I don't think that's possible, since if the boss has that much HP it'll also be strong enough to kill you. I don't think I've ever fought bosses for longer than 12 minutes, so I'm not sure...
Anyway, BP regen resets whenever you gain or lose BP. So if you do a 1 BP raid for 11 minutes and another 1 BP raid afterwards for 11 minutes, you haven't gained a BP tick. You'll be 9 minutes away from it. So an infinite chain doesn't really happen.Use whatever element you can cover debuffs best with.