I like to work with stock rather than diluted developer but I'm having a problem believing that the number of films that can be put through 1 litre of Xtol is more than twice the number that can be put through the same quantity of D76.
According to Aschell & Troop the capacity of 1 litre of D76 is seven films '...if you choose to reuse D76 without replenishment, develop a maximum of 7 rolls per litre.' (The Film Developing Cookbook, p.43). However according to Kodak 'The capacity of the full-strength developer with normal, unreplenished processing is approximately 15 rolls of 135-36 or 120 film...' (Kodak Professional Xtol Developer, March 2008. J-109).
Any comments on the above, particularly from those who have tested the capacity of either developer, would be most welcome.