No I just blow shit up. Didn't read most of that past "shouldn't kill every boss". Sorry. (Just joking, but the point's there.)
Age of the boss doesn't matter. Level doesn't matter. Time left doesn't matter.
I don't even share my event bosses. I just nuke them unless I'm in Discord. In which case I announce then slow nuke, for my online allies.

Not my ally's spawn, I nuke. I don't ever experience event currency problems. I just like nuking.