I've been wondering how a marginal amount of weight affects distance, let's call it the Marginal Length of Weight (MLW). It's units would be measured in miles per pound (kilometer per kilogram).
It seems to me that if I reduce my gear weight by 5 pounds that I should be able to do more distance within the same amount of riding time and exerting the same amount of effort (measured by fatigue at the end of the day).
I don't usually weigh my gear these days as I pretty much take the same stuff on every trip. But, I do know that when I'm not carrying camping gear (13 pounds when mailed home from Jackson, WY) that I am less tired at the end of the day.
If I had to guess, I would start at 1 to 1. That is, every pound of gear I lose is one more mile a day I can average.
I have never tried to quantify it and was wondering how the rest of you would estimate this ratio.