First, for most people, older doesn't equal flatter, thanks to our developed palates and the availability of good beer.
Second, as we age, there is a point that our muscles will not have the same elasticity and function that they used to. Most of that can be put off much farther than common wisdom by adopting a strength training regimen until you die. Breathing is all muscles, too. Could it be possible that flatness is due to weakened air support?
Third, maybe your soft palate has become more and more open over time, the way you have to stretch a bit to play down into a 1+2+3 valve combination on many horns. Maybe it's passed on to the rest of your playing.
Fourth, … oh, wait, no. Most people prefer warmer weather as they age, I believe. Scratch that idea.
I'm sure someone who knows what they are talking about will stop by any minute.



