Even if DMM has more content, the content is static. Its there and thats it. Nothing more will be added as the core and add ons of the game have been all fleshed out.
If the game became boring to you once, it would happen again eventually. You would enjoy the new content for another month or so, and then once you would experience everything there is to it, you would more likely than not get to this point again, where you would be like "soo uh... is that all ?"

I mean, I dont judge or anything, but if thats what counts most for you, then there are some amazing games out there that keep pumping out new content on a regular basis all year long. Though, granted many of them are MMORPG or Indie world crafting games.

With all that said - I do agree that It would be nice if more of the DMM content got implemented into the Nutaku version. Who knows when all of that is gonna happen heh.