Tension in Euc. logs.

A few months ago, I was given two Spotted Gum trees. A few days after cutting them down, I cut up a couple of logs and the boards came out extremely bent. I let the logs lie for about 6 weeks and then cut up a couple more logs and the boards came out reasonably straight. Some species of trees saw up much better than others. Hoop Pine, Red Cedar and Euc torelliana seem to be good while Flooded Gum is the worst I know while Gympie Messmate, the species I deal with most from my plantations is intermediate. My question is, does letting the logs lie for a little while reduce the spring as I have experienced? In other words, if I want some straight boards from my GM plantations, am I better off cutting the trees and letting the logs lie for 1,2 3 months, or even longer before sawing?
I have noticed on the Lucas mill promotion videos where they seem to be cutting Euc. logs that the boards all come out straight. The logs seem to be a little old because the ends of the logs have some checking. Another important factor is probably the age of the the tree. I suspect that older trees have logs that are more stable and cut straight while younger fast growing trees are much worse. My GM plantations are up to almost 40 years old which for trees is not really that old while the youngest that we have sawn is about 15 years old and surprisingly, these few younger trees have sawn acceptably. Cutting longer boards is always more difficult as well.