I understood the seven day set was designed for the privileged and upper class who had, at their service, a valet who would lay out the days razor for the master to shave with or, with which to deliver the shave for him. The fact that the valet had the other razors out of service allowed time to hone and prep them.

So, maybe a two day set was for those who were 'up and coming' ?

Either way, right or wrong, I can't see any reason why a razor would need to rest for 24-48 hours other than allowing time to service the other razor(s) in rotation.

But what do I know...