[jpmoral]

The posts I was replying to talked about 'keeping in the brain-attic tools which may help do work' and 'real, tangible, applicable skills'. That's a different definition than what you're proposing.

Different people will have different definitions of useful. And different people will weigh usefulness differently in determining value.

My point is that I don't need to find some arbitrary definition of 'useful' to cover something in order to find it valuable.