At the time, I have a generic two reel processing tank. It holds just shy of a liter of chemical. It's the one 120 or two 35mm reel kind. I have been using the 5 liter jugs and mixing XTOL, and recently DDX (1:4). The thing is, I'm not familiar enough with shelf life, or replenishing, enough to know what I'm doing. So to be safe, when I develop a roll, I discard the developer instead of putting it back into the jug. I got sloppy with the XTOL and would put it back into the jugs for a few times and took my chances, but I don't want to do that with my project film. Since I'm trying to shoot more, and I'm developing regularly, I have learned that this is going to get quite expensive fairly quickly. I just bought the $17 bottle of DDX a week or two ago, and after only three rolls, it's time for another. What can I do to reduce the cost, in terms if making this last longer?