What, in your system, have you owned the longest?

My amp acquired in 2004 it's a custom stereo tube amp from Deja Vu Audio in VA.

Purchased in 78 or 79.  JBL 65. and McIntosh MA 6100 from Moe’s Sight and Sound, Casper, Wyoming.  MA 6100 being refurbished.

SOTA Sapphire.  Early 1980's.  Suitably upgraded over the Centuries.

We moved 10 yr ago, and I started over as far as most of the gear goes.

What I've owned the longest are some acoustic treatments (15 yr) and two JL Audio f112 subs (13 yr). Next is the equipment rack (9 yr), and after that the speakers (6 yr).

Hales Revelation 3’s