The longest you have owned any gear?

I bought the Ohm Ls currently in my family room in 1978. The Dual 1264 also in there in 1981.

Vandersteen 2Ci speakers for 23 years.  Bought them for 1250.00 new and sold them 23 years later for 450.00.

McIntosh MC2105. Over 40.

I still have my:
ARC Dual 75a- it was refurbished about 15 years ago and is presently not in use- purchased new in 1974-5;
Quad ESL- refurbished recently and now in use- purchased used in 1973;
Technics SP-10 turntable- refurbished and ready to go in vintage system, purchased new in 1973;
among other odds and ends, e.g. Decca Ribbons I purchased in the mid-’80s, Quad II amps I purchased almost thirty years ago (they are from 1961) and recently refurbished and in use in my vintage system; I still have the piezo stylus gauge (with box) that was sold by Technics. Much other stuff that I owned back in the day, new, was traded in for upgrades, e.g. ARC SP 3-a-1 for SP 10mk ii.