by chess trainer, i'm assuming you mean tactics trainer. it works on a time limit also. if you solve the problem but use more than the average times it takes other's to solve it you will still lose rating points. my advice is to ignore your rating in tactics trainer and just focus on getting the correct move.
the reason tactics trainer uses time as a factor is because they needed a variable to construct the ratings for the questions. i agree that it's not ideal, but again, your rating shouldn't be your primary goal. learning tactics and being able to identify them is.
I am relatively new to the nuances of chess. One thing I am struggling with is the concept of time in chess. Not even just per single game, but for example, how ratings work, chess trainer, etc. I posted previously about my opponent being timed out on a game where I had only a king left. It was a draw. I understand that now. I played sloppily and was penalized for that. My sloppy play was trumped by the lack of time by my opponent. Now, I'm using Chess Trainer, and my rating goes down, even if I solve the puzzle, because I took too much time. What does this say? Does this say that the rating is not important? Why would the rating go down if you solved the problem correctly. The game is not supposed to be about time, right? I learned that from my timed game when I drew when my opponent ran out of time. What is the roll of time in chess?