Few (if any) games can support hardcore players at several hours per day over the course of months [i]without[/i] employing those "addictive" features. It's a design quandary: how do they manage a finite amount of content to satisfy a community with a limitless appetite for relevant gameplay? Before making a purchase like TTK, I need to ask myself "if I only play through each activity one time, is it worth it?" If yes, then a progression system that rewards continued play is added value. If not, it will cause feelings of "grind" or fatigue in repeated activities.