I agree with PTOEguy. There are many factors. This subject is popular in the guitar and violin world as well. Strangely, clarinet players do not talk about this process (the best clarinets are solid wood). I also found a thread on a classical guitar site that delves a bit into this.
Here it is.
I had the best clarinet luthier in the known world today work on my instrument and the first thing he did was ream it out. I cringed and almost cried, as I saw the dust from the bore of my clarinet falling out onto the table. He said that, over the years, the bore gets smaller as the wood changes and expands. This can affect tone and intonation, along with other variables.
I said that aiming at this, I wonder if there have been any studies about what exactly happens to the wood as the ukulele ages. The wood and the oils, moisture, cell structure - all of that changes over the years. The mahogany used to make a Martin ukulele 60 years ago. What happened to the remnants of the tree that was chopped down. It rotted away in the forest. So, a luthier takes that wood, prepares it and turns it into a work of art, but that living tree is still chopped down and the wood is still undergoing a process, right?
I'm rambling, sorry.