The longest you have owned any gear?

10 years with a Valve Audio Predator. Still own it but Esoteric separates have replaced it. I will set up a 2nd system with ATC SCM 7v3's.

Pioneer TX-9100 tuner. Since 1974. Haven't used it in years. Cannot bring myself to sell. Way too beautiful. Way too memorable. 

https://stereonomono.blogspot.com/2015/04/pioneer-tx-9100.html
And something tells me, if I ever do a little refresh and hook it up, it will put streaming to shame.

https://audiokarma.org/forums/index.php?threads/simply-unbelievable-tx-9100.55353/page-2

I'm definitely not going to win the "oldest in-use component" prize here lol. In my current main system: Tannoy Canterbury GR speakers, 5 years. Out of all the gear I still have that I might actually sincerely use again: my SOTA Star turntable (now upgraded to Nova V), 14 years. BUT I've at least been rocking Tannoys as my main speakers for 15 years; my love for them has been consistent and unwavering since my early speaker setup days :) And Koetsu isn't too far off that metric either; one of them has been my main source/cartridge for 11 year now. 

Luxman T2 tuner bought in 1972 still plays occasionally.

I still have my wonderful Epos M22's from 2005.  They have played great music and served me and my wife well.