How old is too old for a Dac?

The Redgum sounding very good doesn’t surprise me.  Solid engineering principles are to a large degree timeless.  Well thought out robust power supply and  quality analog output stage are essential to obtain upper tier sound performance. 
Charles 

Great find redmosessc!  A lot of great older used DAcs available for one playing redbook cd files and owning a good USB/SPDIF converter. I currently own four non USB DACs and two converters. 

@ charles1dad

Makes sense. Though not sure how one would go about discerning one from another unless one happened to be privy to the materials used. 

I’d say by the time you're 90 you’re too old for a DAC.

Does anyone have an opinion of the Cal Audio Labs Sigma II? I’ve had one since I bought it new and have always run it with NOS tubes and loved it but I’m wondering if one of the newer DACs under 1K would be better due to the age. I'm particular to tube-based to tame digital for my ears.  It’s not real easy to audition something like this since they have to be ordered online most of the time.