A couple of years ago I had a good sort through all our bedding. It was a moment of super-organisation for me, putting all the ones we use rarely (i.e. for visitors!) into bags and sticking labels on so I know what is in the bag. Astonishing organisation for me - and, it turns out, essential if you want to find a spare sheet in a hurry when one of the kids has vomited repeatedly all night. Knowing that a sheet is single or double, fitted or flat, or even (actually) a duvet cover is remarkably useful.
With the various moves since then there was an entire box that had not been touched and at the weekend we finally got round to sifting through the unpacked box of bags. Now, what I didn't mention above was that I didn't go for fancy bags, or special storage, for all these spare sheets. No: I reached for the bag of carriers and (it turns out) Tesco and Sainsbury's.
Our supermarkets are always telling us to re-use their bags, sometimes offering money back if you do. There is also eco-pressure to make the bags biodegradable, so they don't clog up landfill sites for ever and a day. So here is my non-scientific study of the durability of their bags.
So, if you want strength and durability, go to Sainsbury's. If you wish them to degrade and fall apart, try Tescos.
Or, better still, buy a jute bag and keep reusing it. Even when degrading it must be more environmentally friendly than the flakes of Tesco bag I keep picking up off the floor.