I let the ex calculate the logistics on that one for her and the girls.
One roll of the commercial John Wayne TP a month, and I'm good to go. ;)
10 years is 120 rolls.
/johnny
One time, I put fresh TP in the three bathrooms, and after one week, I checked them, determined how much that was and got a total for a year. That was for husband and me.
Sent that total to a lady friend of mine and she said no way could she and her husband get by on that number.
Conclusion is, TP is an individual number for each person - no size fits all.