I'd like that as boulders and trees survive over the months (and years maybe??) that their rewards gradually increase.
Suppose that as a tree hands its first quest it begins a clock, and as the tree ages its rewards increase and scale with the age of the world.
1 week, approx. 200LP
4 weeks, approx. 2000 LP
12 weeks, approx. 15,000 LP
and so on and so forth, until it plateaus in a balanced way.
The longer a tree / boulder lives, the better its reward, but once it's chopped down, its gone and you have to hope there's another to replace it.
This makes it in some ways meaningful to strive to protect some older relics of nature.
Who knows, it might be fun and its a questing mechanic I don't think I've ever seen done.