Ok, typical new boy question, but I've recently started developing my own b&w negs. Great fun, but I started slowly with one film at a time. The other day I did five rolls one after the other, and the dev looked decidedly murky afterwards. Question is; how long can you expect dev to last? (HC-110). I work in pre-press, so have experience with chemistry and know it must be a function of time and use, but the chemistry at work is far different from b&w, so I'm not sure. Maybe I should just keep using it until I ruin a film, but I'd rather not. Do you mix up the entire bottle and keep it till it's used up? Or do what I've been doing and mix up 300ml at a time, and then throw it away? Any help appreciated. Mike.