I don't think Tactics Trainer helps one's long term abilities to calculate moves ahead, or see checkmates.
No problem! Anybody has his own opinions. Most professional players think the contrary, but again, maybe one can improve his chess in different ways. Also, if your purpose is to improve a meaningless TT rating, I think that you are justified to have such opinions.
I started doing 25 a day since December. Within a week I hit around 2150. I stayed there for another week,then got a string of problems I just couldn't do, also another slump earlier this month. Now I'm struggling to maintain 1800. I have no explanation, just an observation that the slumps in TT coincides with slumps in play.