We have a king size bed with a superking size duvet and have done for 20 or so years. Had three bottom fitted sheets from HoF for years which I used to just put on without thinking about it. They eventually got a bit raggedy so I replaced them about 4 years ago. And have re-replaced them about three times since as they never seem to actually fit after about three months. The current ones are from Next and I went for deep ones thinking they’d have a bit more give. They can’t be more than 6 months old and, even if only the same two have been used, won’t have been washed more than a dozen or so times. I got so frustrated changing the bed at the weekend that I got DH & both DC taking a corner each and, after much battling, bending of the mattress, blaming of each other & so on, we eventually got each corner on. The corner under my pillow had pinged off by the time I woke up on Monday and I haven’t managed to get it back on and now DH’s side has done the same. This is ridiculously. We’ve not done anything which would put undue stress on the sheets!