I'm afraid you're right... most of the Autometer gauges that I have in the car now, I actually bought in the 1980's and they work just like always. Of course they're all mechanical (vacuum, oil pressure, coolant temp, and speedometer). The only one I've been having ongoing problems with is this more recent purchase (~ 3 years ago).
I also didn't mention that this is the second gauge/sensor (the first one stopped indicating at all after less than an hour of run-time, so I Summit replaced the whole set for free). THAT is an example of good customer service!