DAC designers have more than a passing knowledge about resistor load stability and incorporate end of life tolerances in their designs when choosing the initial or purchased tolerance. In other words, they listen and evaluate before they put it on the market.
Downside to R2R Ladder DACs?
A sales person I generally trust told me to steer clear of used R2R DACs, since their reliance on high precision resistors causes them to sound best when new, and degrade fairly quickly. It seems reasonable; have others had any experience with this?