I have always wondered the purpose of 7-day straight sets, is there any other purpose than the novelty having a straight for each day of the week?
But this site breeds Acquisition Disorders. We're never quite pleased with what we have.
I've also heard that multi blade sets were used by barbers.
Guys who tended to do a lot of shaves in a day.
They would have two sets, and send one set out to be honed while using the other set.
don't know if this is true or not, but it makes a good theory.