I've been using a pair of 3.5R's for almost 11 years (purchased new in Aug. 2004). I don't push them hard (driven by tube amps). They sound as good today as when I first purchased them. I used a pair of MG-IIIa's before that - same thing (had them for eight years - also tubes). I suppose if you really drive them hard, for long periods of time, you might need to replace the ribbons. Based on my experience, I'm quite satisified with how they sound as is.
