I think a part of this eventual wear-and-tear comes from the content cap in the game. I feel that by repeating the same tasks out of necessity that we otherwise wouldn't have, we start getting very frustrated with things we otherwise wouldn't have.I was blown away at the start but the more I get frustrated with the shortcomings in the game and other issues the more the allure wears off.
At least with myself, the high I hit at the start of the game and during my exploration of the new content didn't start to waver until I hit the level cap, completed everything there was to do at the time, and started running out of new loot to obtain (at least, started to continuously get repeat loot and upper level loot. I could be very unlucky and am just missing a reservoir of random loot I haven't received yet).
I feel that in the full game, always doing new things, gaining new levels, sub-focuses and abilities, and especially always being able to obtain new usable loot, will help fend off that wavering period.
Unless of course your issues are with the game-design and fundamentals, in which case everything I just listed won't improve the game, unfortunately.