I can definitely understand that. At this point, what keeps me playing is less the game itself and more the fact that it's a chance to play co-operatively with friends I now live about 200 miles away from. I keep things somewhat fresh by using different weapons when I can. I limited myself to only the hammer and the insect glaive during my initial playthrough, so that I could prolong my interest by taking on more weapons later on. Now I'm experimenting with the bow, switch axe, and a couple others, which helps make fights a little more exciting.
If I were playing solo though, I definitely would have moved on by now.