I don't see anything in the newer models to suggest that they will last any longer than the Aquastar and Paloma Pak units. Most of them made it around 10 years.
And you determined that by...
... market survey???
I know of two E.L.M. Aquastar (pre-Bosch takeover) that are still in service with 15+ years on 'em. Don't know of any that out & out died or needed a heat exchanger swap, but it's a pretty small sample size (and only one can I claim the installation on.) They're somewhat finicky PITA units with mechanical feedback that doesn't really modulate well, with a propensity for overheating then self-extinguishing at low flow, but they just won't die (as much as the current owner of one wishes it would.
) I think of them as "reliably finicky".
Maybe I live/work in an area with fewer water-harness issues or something(?).
But the newer versions have both much higher efficiency and higher complexity. Their true track record is still being made, but the Rinnais & Takagis I've encounterd over the past 5 years all seem to be in good shape and running without problems. (I understand that some people have run into issues with Takagi flame-detectors, but I've yet to see it in person- perhaps I will some day...) Again- a relatively small sample-size.
I've yet to encounter anybody who replaced their tankless with a tank (except a few of instances where they were upgrading heating system boilers and went with an indirect-fired tank, which is the best of both worlds IMHO.) Have you?
I've read of people who had been using them as hydronic boilers trading up for mod-cons though.
They may not be for everyone, may not be cost-effective in low-cost fuel markets, but people don't seem to trade 'em in, and live with 'em despite their quirks. Hard-core greenies seem enamored of the operational efficiency, but that wouldn't describe the average tankless owner in my neck of the woods.