The first sentence, the noun is plural. Christmas trees. The plural trees don’t singularly live one life. So the first sentence doesn’t make total sense Christmas trees live a happy life. We’re going from plural to singular. So the second sentence makes more sense. Christmas trees don’t live good lives… the plural nouns have a plural object: lives…. Sounds more correct.

"Christmas trees don't live long." That is all I'd say.

Both sentences sound OK to me, but I agree with Charlie that the second one is technically more correct.

I think you could say either, Sergii... The second one does seems more logical/ more 'correct' (plural trees/ plural lives), but I'm pretty sure you could hear the first version equally often. It's probably a bit like, "The government is..." vs. "The government are..."