I just sold a 20 year old synthesizer, in perfect working condition, an electronic device, for 1/3 of what it was worth 20 years ago. This was a digital instrument, if it was analog it probably sold for more than its new value (vintage equipment). In my experience, electronics last at least 10 years (my laptop), but it is the mechanics that degrade over time (pots, switches, jacks). I have a 66 year old tube radio, a 40 year old VCR, a +30 year old amp, all in fine working condition. As for a digital accordion, I suspect that its mechanics will fail before the electronics.
And "old technology" may be perfectly valid for smartphones or laptops, but not to the same extent for electronic musical instruments (of course, there are technological advances made).