My DPs stayed in their 3-bed council house until they died, some 15 years after my brother left home. However, they were in the early stages of dementia when he moved out and never would have coped with moving to a new area, and there were no smaller social housing properties around where they lived.
They'd been in social housing for nearly 50 years, always paying full rent, and had probably repaid the cost of building and maintaining the house over that time. I'd have preferred them to have moved, tbh, it would have forced them to get rid of all the stuff they'd hoarded over half a century and saved me spending a fortnight doing it after they'd gone.
My MIL is still in the 2-bed council house she moved into in 1961. She'll never move, she's spent all those years creating the most fabulous garden (over 100 different varieties of roses) and it would break her heart to leave her life's work. She's amazingly fit for an 87 year old and in full possession of her marbles, and if the council tried to force her to downsize, her adult kids would help her exercise her right to buy it and pay for it themselves. She gets full housing benefit (no "bedroom tax" for pensioners), and has done since her husband retired nearly 30 years ago.
In principle, I think it's wrong that older people are occupying much-needed family housing, but when you look at individual cases, it's also asking people to make massive changes at a time in their lives when that is most challenging. And of course, if successive governments hadn't failed to build social housing in any meaningful numbers, the debate wouldn't be necessary.