What I've been doing for the past while is use stock D76. I pour the D76 in a liter bottle, and when I develop my film pour as much as possible into my 2 roll patterson tank (it takes about 850ml or so). I then develop and pour it back into the 1L bottle. I process 5 rolls this way, and then throw out the developer; I don't increase the development time. I find that across the 5 rolls the development is very consistent.