How long do you or should you keep your gear.

I occasionally remind my wife that I don't hunt, fish, nor go to casinos..  And I tend to replace my audio equipment very infrequently, so I'm a relative bargain.  😄  I just replaced 31YO Counterpoint amps with PrimaLuna EVO 400 amps, but I kept my 31YO Dahlquist DQ20s, as I didn't hear anything compelling enough to replace them (without spending $20K+)..  The addition of a Rel Acoutics 8/12 subwoofer facilitated that decision.  

Rather than how long does one wait to chuck stuff out, a more interesting question for me is how long does one wait to release/buy new (not necessarily better, could be just another version, perhaps worse) technology.

They are two completely different issues.

Another alternative, Carlsbad, is to focus your time and energy on improving the sound produced by the gear you already own.  This can be a lot more rewarding and considerably less expensive.  A different kind of challenge...

Ariston RD11S in use since 1977! Original belt still good - it gets an occasionall wipe down with Armor All. Presently has a Grace 707 arm/Denon 103 cartridge mounted.

In 1980 I bought a JBL L212 system (3 speakers including a 12 inch sub).. They were about 2 grand, and I thought they sounded incredible..  Amps, dacs, turntables, have come and gone, but I still have those speakers, and love them as much as day one.