Like you Sm, I owned a pair of Infinity Reference 60 speakers for 18 years before I sold them. They never skipped a beat in that time & still looked mint when I sold them. Though the original foam bass surrounds on the two 8" IMG woofers were drying out and becoming deformed (which is to be expected), resulting in distortion. I would have also expected the caps to have degraded & the internal Monster cable to have become somewhat oxygenated.
In saying the above, it's all relative. The Ref 60's were only $2500AUD way back when, and obviously capacitors, inductors, OFC wire and speaker surrounds have all improved significantly since then. Therefore I would expect a pair of good hifi, or high end speakers to last >18 years these days. How long would vary from speaker to speaker, though if you're paying big $$ for high end speakers you should rightly expect to expire before your speakers do!
