The longest you have owned any gear?

Simple.

Oldest (47 years) - Teac 4070 Auto-reversing Tape Deck.  Just had first tuneup.  Has always worked, and well.

Second Oldest (42 years) - Original Dual 701 Automatic Turntable.  Survivor of a shoot-out with my Linn SP12 / Syrinx arm combo.  Same mid-range, better bass, acceptable high-end.

Third Oldest (38 years) - ARC SP-6a.and Marcof PPA-2 headamp w/Moncrieff mod.  Recapped.  Noisy controls, but sounds sublime. Retired my 2004 Margules transistorized preamp. 

A Counterpoint SA 3.1 preamp I bought in 1986 and shelved in 2016. 

A pair of Sonus Faber Minuetto speakers I purchased in 1993 and sold in July of this year.

A linn LP12 ; 37 years and still spinning....Ls3-5a for 23 years....

In a few short months my Wilson Audio Watt speakers will be 30 years old. The serial numbers were so low, I know Dave built these in his garage. Over the years I had the xover upgraded to series 2's, purchased the puppy cabinets, then also upgraded those to series 3. More recently  they needed new tweeters, new baffle foam, and new grilles but by and large they are in amazing shape and they still give all of the Wilson "Magic".  Numerous cd players, dacs, pre and power amps have moved thru my room, and these speakers have grown and shined with each upgrade in front of it. As I look back and listen, Dave was years ahead of his time. A Wilson Audio product is truly is a lifelong investment! 

I am still using an Adcom GFA 555 in my current home theatre system that i purchased new about 28 years ago. This amp has been incredible throughout the years without having any problems what so ever or needing circuitry upgrades. I also have 2 other Adcom GFA 555 II amps also pretty old still cranking out powerfully in system as well.