Wood being wood and LOTs of shooting, wood changes over time. This is not all my bows, usually once they settle in they are good to go, I may have them drop a few pounds or take up a little string follow but not get out of tiller.
The rock hard osage with a good early wood late wood ratio seems to be the most stable over time. I do make bows with osage that is much less dense, these seem to need a little tiller tweaking over time, the last one I corrected took ten years to be troublesome,