The longest you have owned any gear?

Thiel 02 speakers owned since 93.  Though I've moved on to many other speakers, floor standers and standmounts, I can not get rid of the 02s because they re-ignited my interest in high end audio (they were my girlfriends-now-wife).  They have a magic that still serves as a benchmark for me.

Other than that: custom built tube pre-amp from mid 90's, Conrad Johnson Premier 12 amps from 2000.   Spendor 3/5s bought in 2001 still doing duty as TV speakers, and occasionally take up residence in my 2 channel system.

36 years ago in 1981 l purchased a NAD 3040 that still powers my garage/outdoor system through an outboard preamp.

With respect to bondmanp, I stupidly sold my Thorens TD-166 MkII when CD players became popular.

Pioneer SC-700 preamp and Sony TA-3200F power amp, both bought in 1973, both still in operation.

Air Tight ATM3 since 1996.still in use today. One of the mono bloc has been for repair 2 years ago (timer for tempo needed to be fixed). 
Too bad 😀