When I rotate razors, I feel that if a blade has been used and then sitting for a few days I don't get as many shaves out of it total. Has anyone else experienced this phenomenon?
I believe it's down to microscopic rust/oxidation that is the main enemy for blunting blades prematurely.
I have a mate that lives up north and relies on a underground spring for water supply, plus the air quality is very good too. This water is just about as pure as you can get.
He's on 20 plus shaves with a feather at the moment, this being his only feather as I gave it to him weeks ago and when visiting him last I had look at the blade and it looks brand new, curiosity got the better of me so I had a shave with it and received a dfs. The only thing that this can be put down to is the quality of the water. I would add that I only used Pears glycerine soap to lather up and this produced a great lather, I'm putting that down to the pure water too.
The kind of water you describe. coming from an underground spring, may taste wonderful but invariably has dissolved minerals.