Fellow asthmatic here:

>I should have thrown away my inhaler years ago because I was never using it?

Inhalers expire after a year, so yes, you should have, and you should have gotten a new one. I only learned this after getting a fresh one at the start of COVID because I hadn't had one in several years. Pretty sure growing up I had the same inhaler for like 8 years, so obviously it still works OK after a year, just relaying what my doctor told me 5 years ago.