The maple fades with time, like the cherries in Smokin Cherries. It's still good, but less maple. Have you noticed mature MB has a little whiskeyish touch, like the maple is fermenting?
The aro that really maintains its non-tobacco flavor is Cocoa Blend, I think. The more that cocoa relaxes into the mix the better it becomes as a foil for the tobacco. But, hey, I like 'em all!
I've definitely noticed something like you described in the maple and never would have thought of that description myself. Ha! For my tastebuds, the maple wasn't that strong to begin with (uncapped May 31). It's delicious, for sure, but for some reason I thought this would be as sweet as Vurley.