As we age, many of us go back to what gives us comfort. And for many of us who love music, it's often the music of our more formative listening years, whatever style/genre that may be - hard bop, Armstrong, traditional country, classic rock, old school R&B, whatever. I'm not sure that's quite the same as getting more conservative, ears-wise. Maybe it is. Or maybe if you started out with a love of diverse sounds and styles, that continued exploration is your comfort zone. So maybe continuing to do what you did earlier is a form of conservatism, since you're not changing and evolving, despite continuing to listen to new things. I dunno.
Outside of music, I've noticed many of the people I knew when I was younger have become more and more conservative (politically, culturally) personally as they age. I have less and less in common with them over time.