Is there such a thing as a FOREVER DAC/streamer?

I believe Esoteric’s have firmware that can be updated.

I would say that for those 75 or older, a DAC bought today would likely be FOREVER.  Below that age it will become outdated.

@kota1

I have always found plateaus that I am really happy with for seven to ten years. Where I have no interest in upgrading… I don’t want to screw up the synergy created between all my components. I read The Absolute Sound and Stereophile… etc. but have no desire to upgrade… just enjoy my system.

Then for no obvious reason I get interested in upgrading one piece… the one I perceive to be the biggest opportunity. I never do less than 2x or 3x investment so it makes a significant difference. But that triggers upgrading many or most components… then interconnects and power cords, then vibration. Then I am happy as a clam for another 7 - 10 years.
 

Clams are happy? Why is that?

@gpixels 

That is purely a subjective question, it depends on user preference.  Spend more you’ll get more.  If one is satisfied with the sonics and/or $ spent then likely they will stop.  
Digital audio, like most technologies, does not stand still.  

@ghdprentice , you find you groove, you know it could be "better" but there is always a risk it could be less enjoyable too. I found that once I got my room just right and upgraded my room correction software, my system was "good enough". Thanks to other members here I learned that to get a decent step up a better dac would be least $5K and I still don’t know if I would prefer it over what I have now, maybe it would be not as good a fit.