"But won't you get BOOOOOOOOOOOOOOOOOOOOOOOORED?" is what I heard most often. I suppose I asked for it, because whenever anyone asked what I was going to do when I retired, I'd say, "Nothing. I'm going to do nothing. I've never had a chance to do nothing and I'm looking forward to it."
My mother, who was most begrudging despite having retired herself in her forties, got her ears blasted off for persistently implying that she believed me to be nothing apart from my job. When I mentioned some post-retirement freelance work she was like, "Oh, your new job, your new job, when do you start your new job, new job, new job, tell me about your new job, are you sure you'll earn enough in this new job, are you sure you won't have jumped from the frying pain into the fire? So, about this new job of yours, how many hours is it ... " and I was having to say, several times a week, "MUM, I'M NOT GETTING ANOTHER JOB, I'M RETIRED." And then the kids would be 'phoning and saying, "Granny tells me you've got a new job, Mum. What's that about? Why didn't you say anything to us?"
Most folk have just assumed I know what I'm doing and minded their own business. Colleagues said, "I couldn't afford to retire," and I'd say, "We can only afford for me to retire because we can live on almost nothing," while silently thinking, "You've earned at least as much as I have over your lifetime and I haven't made the smartest financial decisions along the way, so why can't you afford to retire?" But I know it's largely because we've become accustomed to living well below our income and they'd have a lot of psychological catching up to do.
My widowed FiL made me smile. He was never comfortable with the arrangement whereby I worked and my husband stayed at home. When told I was retiring and DH was going to continue to work for a while, he declared it to be only right that The Man should be out working and The Woman should be at home. He's happy to assume that my freelance work is just a bit of pocket money for me and his son is paying all the bills, and we don't see any harm in letting him believe what he wants to believe.