I normally have one pack open in each of our two loos, and at least two unopened packs (of 9 rolls), so one pack in use and one spare for each loo. This is my minimum comfort zone, as soon as I open a 9-pack, I put another on the shopping list, but when they're on offer I may well double up on replacement packs. It's not as if they have a use-by date!
I do exactly the same with the other items people are stocking up on. One pack of paracetamol (and one aspirin, one ibuprofen) open downstairs, one open upstairs, and one in my bag - and therefore three more packs on standby at home, ready to replace each open pack as they're finished. And 4-packs of tinned tomatoes, 3kg bags of pasta, laundry powder, soap and shampoo, milk, butter, cheese... always one open and a minimum of one ready to replace it. I'm over 60, I've always done this, and I honestly can't imagine being down to my last one of anything - well, anything I get through quickly. I don't keep a spare bottle of soy sauce, for example, because I don't use it much and a bottle will last a year or more, but there's a spare ketchup, HP sauce, mayonnaise... when one has enough for a couple of weeks left in it, I put it on the shopping list and can look for offers or the best price to get another one before the open one runs out and the current spare is started.