A bit of geology!
@dancerinthestorm I thought it would a bit easier to answer here.
So these are really still growing? How fast do they grow? And will they ever stop?? And what would be “old” mountains by comparison???
Yes, the Alps are still young and growing mountains. They started around... more or less 40 or 50 millions years ago with a peak around 9 millions years ago. It's relatively young compared to other tectonic features in the world. Just the Pyrenees are older with a start around 500 millions years and "growing activity" around 50/40 millions years ago
(if any geologists want to correct my dates, please do, it has been TOO long since I studied those ranges so my apologies if the date are not quite right).
The pace at which they grow depends on the tectonic activities. Once again, if I remember correctly, the Alps growth is around a millimeter per year. It's not much but that's geology for you.
Mountains can stop growing if the tectonic underlying their original appearance either changes or stops. The Appalachians in North America are older (480 millions yo... if I'm not mistaken). When a mountain stops "growing" the natural erosion (which happens all the time) will slowly smooth them down, giving a more rounded aspect to the range.
The oldest range (I had to look into that) is (if I believe Google) Barberton Makhonjwa (South Africa) or Hamersley Range (Australia) with age around the 3 Billions years old.
Let me thank you to allow me to nerd out a bit on something I love and studied when I was young.
When hiking, know that each rocks you see has a secret history to tell you. Its origin, how it appears, was formed, came out of the depth, was folded... and everyone of this details will help you understand how the very landscape around you was born.
Geology is a way of seeing the world around us and to learn its history.