Downside to R2R Ladder DACs?

bs meter from that salesman just hit 100

suggest u trust him less going forward

Just to chime in on salesmen BS... I recently had this salesman suggest I’d buy his Audiolabs MDac because the other DAC I wanted to try out somewhere else was sounding worthless. The DAC I was talking about was the RME-ADI 2 DAC...

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.

Since we are an audio manufacturer that builds DHT R2R dacs, this is absolutely false.  That would mean every component would have the same issues since everything has resistors in them.

Dump that sales person.

There is no superiority in r2r dacs, they tend to be more euphonic but sometimes less resolving. YMMV

That all depends on the design of the DAC.

Not true at. All , a quality resistor such as what you see in amplifiers, preamps last for decades, capacitors wear out before resistors , resistors control resistive values and dissipate very little 
heat especially in digital where it is low voltage .i have modded for over 20 years ,just think. How many years you may have Held
onto a a piece of electronics And it still works I have tunes 30 years old still working and quality resistors just  keep doing their job ,look at Vishsy naked resistors for example less then .5 watt
and rock solid used for years and tolerances on average well under 1%, if matched by the hundreds better still and won’t drift for many years wear a capacitor is constantly changing a resistor 
is a constant. I had a AbN 1704 R2R  dac for over 15 years sold it and still working .