Happy to help where I can. I know a little bit about a little bit.
I have been a professional woodworker since I was a teenager, and amateur before that (family business). I did both music and woodworking full time (sic - what can I say...youth) until I was 25, now I am just an amateur player.
Did a union apprenticeship in NY. Worked as a journeyman wood machinist in NY, Boston, and all over CA, working my way up to floor foreman in a union shop. Started my own company and ran it (with much help) successfully for 10 years. Lost our production space, now am Plant Manager for a former competitor. All to say that I have thought about wood movement a bit.
Maybe you folks can help me a bit with my bass playing...
Regarding the movement issue, think about how many door panels you have seen that were cracked. This is usually because at some point the panel got stuck in place (usually with paint or finish) and could no longer expand and contract along its' width. Wood cannot be stopped, so the panel cracks so that the pieces can continue moving.
The issue is magnified by increasing the width of material glued or fixed to an adjacent long-grain component. Here is one place where size does matter. Double basses crack/split more than 'cellos, violins, violas because the tops/backs are simply wider. The whole construction method doesn't account for movement very well. A person can sort of get away with a few inches of width glued to length without much drama, but when you start gluing something as large as a 'cello or especially a bass top to a long-grain rib, it is a recipe for trouble. Because the ribs are curved/angled in relation to the tops' grain direction, it is not quite so dire as if they were glued at right angles. The hide glue luthiers use will often fail before the wood fails, by design.
In other words, DB construction makes very little sense in terms of wood movement, which is why we need good luthiers so badly! Thanks to Arnold Schnitzer et al for being there for us. These brave surgeons keep stitching the patients back together, again and again...
Age doesn't change or stop the movement. Wood recovered from the Pyramids of Egypt is still expanding and contracting with changes in temperature and humidity. "Cut" of lumber has some effect. Quarter sawn or rift cut wood moves less than plain-sawn lumber. This has to do with the number of denser "summer wood" growth rings per inch in the wood. Google will educate anyone interested in the movement properties of differing cuts of lumber. Here's one off the top of a quick search:
http://www.inthewoodshop.org/methods/wwc05c.shtml
The moral is try to moderate temperature and humidity in a DB's environment (or the home of any cherished solid wood object). Use a hygrometer and humidifier. Bless our luthiers, especially we double bassists!