In the PSU I mentioned, the origin is propably from years approx 1992...1996 and those have been also in lab use. So that is pretty good expected lifetime for a good quality multiturn pot. Those old Bourns 3590S seem to be some level touch sensitive, at least when pushing the knob on the axle direction -> occasionally power supply output voltage is lost (I assume the center viper has not contact on wirewound resistor)