well pine is a shitty wood anyway! realism!
but seriously, what about oak and maple then as well? i don't know the exact growth rates (and lets not forget the last stage is dependent on a decay hit coming at some random time). it does seem reasonable for the 3 log trees to have a growth time 1.5x that of a 2 log tree i suppose, but i don't think they should have the same growth rate.
edit:
Avu wrote:Even if they give 4-5 logs firs are still better because they will have double the q...
well this isn't quite accurate. yes, your pines would probably be a bit lower q, but don't forget the seed is only part of the equation. you would still have to consider the pot, the soil, the water, and the herb table.