I used to work with a bloke who made sandwiches and froze them.
He'd get them out in the morning, and they'd be defrosted by lunchtime. He did advise not putting lettuce in them 
I take my lunch to work each day - sometimes that;s a sandwich, or left-overs from the night before.
Don't see any problem with keeping sarnies in the fridge if they still taste OK on Friday. Supermarket bread lasts a long while, I believe?
All a question of taste - I don't like supermarket bread, and my home made bread probably wouldn't last five days. I've never managed to keep any that long to find out!
With regard to choosing sandwiches from a shop - I'd be looking at the use-by date to determine if they were still OK to eat.
Edited: 02/08/2011 at 13:20