I've done my own study on this, it lasted six months for my TP use only. The first three months I had the TP pulling to the left, I used 3.5 rolls per month, the last three months the TP was being pulled to the right, I used 3 rolls per month. All the TP used in the woodlands chitting study was two ply.
about as much has having your t-shirt on inside out. Whenever I see that I think someone is trying to get a second day wear out of it.
The wife always insists on under I personally don't care. I think the next ? should be are you a wadder or a folder? I fold the wife is a wadder!
Finally a poll worth some thing OVER< OVER< OVER>OVER 9 out of 10 times, the wife does it under, next time she does that i'm going to scotch tape it to the roll. Or take off a new roll and keep a 2 paper left used up roll on it.