I love Microdol and have been using it since 1972. It's got the finest grain I have ever seen with the TMax films as compared to what i got with Tri-X or Pl-X in the old days. Film has gotten so much better in that respect. I also find I hve more control over my compensated development times. Although contrast is a bit low I don't mind since i make that up in paper grade.
I do find old developer doesn't work well if stored too long, 3 or more months. Perhaps you should buy smaller packages to make a quart so you won't have to store it. OR the other alternative is shoot more film. You'll get more consistant results using fresh stuff. How is your fixer, maybe your problem is not developer but instead a clearing problem?