What is the average life expectancy of a DAC?

Hello folks, 

With the recent profusion of relatively inexpensive DACs that are now available, I'm wondering what the average life expectancy of a good DAC is? Or, to put it another way, is it cost-effective to invest in a high(ish) end DAC like a Denafrips Terminator or a Halo May with the expectation that it will last at least 5 or more years?

I had a Levinson No 39 purchased in the late 90s. Six or so years ago, I bought a Wyred4Sound DAC-2 based on the positive reviews and thinking that technology had progressed so much that even a less expensive DAC (the W4S was about $1500) would surely be better. Not even close (although I was only using with Redbook CDs). 

I eventually sold the No39 when I bought an Yggy A2 which did sound a bit better. But the main reason I replaced it was that it didn't have USB and at the time I was just using a PC to drive it.

I still own the Yggy, but this is now relegated to a secondary system. I bought a Terminator and then replaced it with a Terminator Plus. 

I think a well-built higher end SS DAC will last for decades and will hold it's own for many years. Will you be able to better the sound in five years for the same money. Probably, but I think the improvements will be subtle. 

The more likely issue will be some new interface that becomes popular that isn't supported on existing DACs. This was the problem I had with the Levinson. 
With a dac there is not life expectancy issues but there are planned obsolescence issues like new technologies and formats that always appear.
What a great question as it addresses both reliability and obsolescence. Imo DAC design and the chips have made significant advances over the last decade. The main concerns will likely result from connections (usb, wireless, ethernet etc) and possible sampling changes i.e. MQA. Buy the best you can afford and if those factors change significantly sell for ~50% of what you paid. You will have had 3-5 years of enjoyment at least. While above my intended budget, I just dumped $6k on a streamer/dac and couldn’t be happier. 100,000 + tracks to explore and enjoy at my fingertips and sound quality close to +/- with my vinyl depending on source quality. If I sell in 4 years at 50% my out of pocket for those thousands of hours of enjoyment is ~ $60/month. Not nothin but life is short and we are all here for the love of music.
I think there are two questions embedded in yours - one obvious, one hiding.

The hiding question is "how long until it is obsolete and [possibly to you] worthless".
The surface question is "how long will it operate reliably".

If you buy a quality DAC at the top of the food chain ( in its range) the answer is "quite a long time". While i have new/newer DACs and prototypes I’m working on (excellent, but have, uh, issues at this early stage, kinda like 2 year olds), i also have two very old DACs and both are useful.

One’s a circa 1999 (?) MSB Gold Nelson, with a bunch of modifications I made that improved it significantly. It works great, sounds "good" but not state of the art, and has a big flaw (to be corrected) - S/PDIF input only - no USB or network.

I also have an even older one; a Theta DS-PRO II from what, 1989? 2nd Gen of the DAC that started DACs. It was also S/PDIF only (duh, i came out when that interface arrived) and continued to sound pretty good. Again the bog caveat was that i needed a USB or network --> S/PDIF converter and most suck. There are a very few pretty good ones, like Mike’s Piece of Schiit, but it doesn’t play well with the Theta - they get in synch fights. Ironic since Mike designed both, albeit 40 years apart.

So i built and inserted a USB --> isolation --> re-clock --> clean power stage before the S/PDIG and stuffed it inside. Now it soudns much BETTER than it did, presumably with less jitter and ground noise.

I realize this is not a path most people can take, and normally i would not waste the time, but the DS Pro is such a piece of audio engineering history (look it up, very innovative and cool) that i just had to save it.

So the moral of the story is that within reason, they can both last and continue to be useful and good sounding - but tech may move on.

Hey if mahler is right on the inflationary cycle ( there is a global chip shortage) might be able to sell for more than paid....ha..
course don’t listen to me I have a Smithsonian basement full of obsolete tech DAT, HDdvd, VHS, SVHS, Nakamichi cassette anyone?