Lately I've been getting little or no stain with HP5+ developed in ABC 1:1:1:10. I dilute it more than the traditional 1:1:1:7 in order to lengthen the development time so that I can develop it longer than 7 minutes or so for a normal negative. Anything shorter than that produces uneven development and mottling. ABC has always produced excellent image stain for me with very little general stain. The excessive general stain obtained with PMK is why I stopped using it. ABC is also more acute than any developer with metol in it.

As to the life of stock solutions: Solution A, when stored in an amber glass jar will last at least 6 months. Solution C, the carbonate, can be left to your heirs in your will. I always mix Solution B, the sulfite, from the powder for each use so that's not an issue. It's only solution A where you need to watch how often you mix up new.