Thank you for this marvellously informative thread!
I know that washing machines have been mentioned a couple of times. Have you had enough experience to know if the machine does the straps any harm?
Have a 1943 and a 1944 on the way, and don't want to damage them! The website says hand wash only, but maybe a gentle cycle will be ok?
The only canvas strap that I have at the moment is this one from CWC. Have been putting it in a 30 degree wash with with Nikwax, not detergent, and it seems to be surviving. However, it doesn't get worn very often.
Cheers!