Roger Hicks
Veteran
For me it's not just the backup, Roger, but avoiding changing lenses all the time.
In an ideal world, of course you're right, but I can't help feeling that this falls into the old sin of 'luxury', which I believe antedated 'lust'.
Also, when I shot only film, I'd have two lenses on two bodies, colour & B+W, and switch lenses. I'm now perfectly happy with digi colour, but for B+W, I regard digital as against the order of nature, aso it ain't that different: M9 and MP.
Cheers,
R.