The extractor fan - pull cord timer type - in my bathroom is pushing on 20 yrs old, and yes, is possibly due for replacement which I suspect will be the logical answer.
Anyway for the past 3 years or so, about once a year its performance becomes erratic and I've found that dismantling down to board level, giving it a puff to blow away any dust and then reassembling solves the problem - for another year !! It could be the magic blow but any suggestions as to why after 15+ years of life.
Rob