I think it depends on how you define "functionality". It is my understanding that the filtering qualities of a "line conditioner" will remain indefinitely. I have been told, however, that the ability of the conditioiner to protect from power surges does diminish over time (which is also darn important) A garage manufacturer of such products informed me that the part (I can't remember the part name) that handles surge protection fails with age and that even computer type cheapy power strips utilize the same technology as is in most hifi conditioners. This reminds me....you can get surge protection insurance from you local power company(cheap) in case of disaster (because home insurance would not cover electrical surge damage).
AC Conditioners?
Interested in a used AC Conditioner but don't know much about them. Can anyone tell me if they lose functionality as they get older? Do they where out? Do they not filter as well after protecting from some kind of surge? What are the considerations and what questions should you ask? Appreciate any info anyone can provide....