Yes, the MM requires a very fine grind. I have thrown out perfectly good MM roasts thinking there was something wrong with it. I usually rest it for 2 weeks as well but that won't change the fine grind required .
A bean requires a change in grind when it needs it. Sorry, that is not that helpful but there are so many variables. Things that will influence grind are
- bean type
- bean age
- brew method
..but you just have to adjust your grinder to produce the required result and only experience will determine the required grind for your equipment using the coffee you have a that time.
What you could try is blending with the MM. Just add a small quantity (say 10 - 25%) to your next roast. This will reduce the need for such a fine grind.