LAIV Harmony

Well, the Harmony DAC has a resistor bank that you could just replace them all in one shot for each channel. A lot of DACs use surface mount resistors and they would be very difficult to measure, and almost impossible to replace on the main board.

I've had two components develop issues due to age. A solid state amp and a tube preamp.  Seems to me that components can fail in any piece of electronics.  I like the performance of my Gustard r2r dac, so I think I'll hang onto it and see what happens. 

No such thing as resistor drift for ladder-type DAC's. They use metal-film resistors - not the old carbon comps. Another non-issue by the neurotically obsessed!

Okay, Bourne, now we’re labeled obsessive neurosis (ON). Yes, metal film or modern carbon composite resistors are resistant to aging drifts, as you said, but they can still suffer permanent changes in value if subjected to temperature or electrical overloads/high voltage gradients. Maybe with good surge protection, this won’t be an issue—but who knows? (another ON thought)

I'm with Jason on this one... Resistor drift is a non-issue for modern electronics and should easily expect a ~20+ year lifespan unless there's some serious abuse involved.

Drift Calculation for Thin Film Resistors

There's much greater precision required in other applications (such as automotive/aerospace applications) and somehow the world still turns:

Resistors in aeronautics applications: Meeting the new performance requirements

I was seriously considering a MSB DAC and in one of their design videos, they state that their typical product cycle is 7 to 10 years.  I can't imagine they'd expect someone to buy their $100k+ R2R DACs expecting it to sound poorly before they replace it with a new model.