I'm pretty sure I have. 5 years ago I was listening to nothing but heavy metal, of all different types.
Since then I've gradually declined from heavy metal to...
-movie soundtracks (Hans Zimmer, Clint Mansell, James Horner, etc)
-ambient
-post-rock (This Will Destroy You is my favorite currently)
-various classical composers
-and even gaming soundtracks like Halo1/2/3 even though I don't spend much time on games these days.
I still like heavy metal, and I still pop in an album maybe a couple times a month in the car, but I just can't listen to it non-stop anymore.
You could also ask yourself the opposite - did you listen to more and more heavy metal as you got older?