I suspect a similar question would be 'How long is a piece of string?
Is toilet paper a western phenomenon only?
Given the apparent lack of toilet paper in supermarkets, it seems pertinent (or impertinent) to ask how long a roll (of given number of sheets; ply etc) would last an 'ordinary' family or person.
Can both sides be used? Can the material be recycled?
What alternatives to toilet paper are there?
What leaves would you avoid (e.g. poison ivy)?
Is there a database for toilet paper usage?
How much can be hoarded before it overwhelms a family?