Guys. I have just seen your replies. Thanks for the information. When I said it 'died' what I meant was that it was not producing the stained negative as it should. I made a new batch as I stated in my original post. I did a clip test with it yesterday and it is still good, at almost 6 weeks old. This version was based on some 'Windisch developer' I had. I increased the cetahol by 2 grams and added the phenidone. BUT I left out the metabisulphite, as it did not appear in the Windisch formula and I think is only a preservative. I also like this developer but I also use 510 Pyro, which has never given me any problems. I will keep testing at intervals to see if it lasts.