It’s been two years since I last ordered my last one, should of renewed sooner, but my wife has to do all the ordering for me and I did not tell her in needed replacing until she noticed my stubble, needless to say she told me off.
I have been using this model of shaver head for some years now, and am always completely content with it. It gives a first class shave straightforwardly with no fuss. (I'm also very well satisfied with Shavers service and delivery.)
I left it 2 years before replacing cutter/foil. You certainly notice the difference. Braun are right when they say 18 months. Used this company for some years now and they always give very prompt and efficient service.