When trying to answer your question, I was shocked to see how many watches have already left my collection, simply because my taste has changed a lot in recent years (decades).
Only in one case not: I returned to the IWC Da Vinci 2nd generation with regret
after parting with the first generation.
Just looking at my collection now the OLDEST piece now that I STILL WEAR from time to time is my Zenith Pilot Montre d'Aéronef Type 20, which I bought in September 2009.
Followed by my Moser Henry Double Hairspring (which I purchased in 2012):
I still own my FIRST “beautiful” watch. I got it as a present from my father. So even if I DON’T WEAR it anymore, it’s a watch I will never let go: a Seiko CJH990 from 1985:
Best
Thomas