The longest you have owned any gear?

Phillips CD-80. Bought it from a local 20 years ago, sold it once and then bought it back from a local audiophile. Original box, papers ,transport screws,etc. May use it as a transport when I get more room.

1984/1985 I purchased my first hi-end system:
Threshold SA-2s, Fet Ten line and phono stages, Sota Star Sapphire with an SME V, Cambridge CD player, McIntosh MR80, and Snell A III speakers. The CD was replaced some ten years ago with an Ayre which I still have in my current system.
The system sounded great up until October 2015 when I decided I wanted a change and went to tubes. My old gear is stored in the basement for my son who doesn't have the room at his current location.

My aiwa ad f770 cassette deck, since 1983 to present. It still works as good as day one, with a new set of  belts. Second I guess would be 2 of the many tuners I own. The marantz st6000 and the cambridge t500.

I still have my Acoustics Research Amplifier, bought new in 1969 (50 years?!).  In active use until it was peacefully retired into storage in 2012.

My Ariston RD11S TT. Bought new in 1977 for $280 w/o arm. Added an SME 3009 and a MicroAcoustics 2002 cartridge. Presently have a Grace 707 and Denon 103 on it, along with a Hiraoka SE-22 mat (bought new in '78 for $20 from Harvey Sound, NYC). The Ariston/SME was purchased from Audiocom in Old Greenwich, CT (best HiFi store in Fairfield County).