You shouldn't spend a lot of time per day on tactics anyways - after about 15 minutes or so, you probably won't be as sharp as when you first start. However, Mentor is geared more towards study, so it's important to take your time there.
Your results may vary, but I find that about 15 mins. per day on Tactics and about 1 hour on Mentor is right for me.
There are a dozen or so tactically oriented courses on CM that you absolutely need to have knowlege of or you will continue having problems with the TT. All the obvious choices in basic tactics, basic checkmates, specialized courses in forks, pins, skewers, discovered check, smothered mate, double attacks, etc. will give you the vocabulary to deal with TT. Some people already have this knowledge and don't need introductory tactics courses to survive or thrive in that environment. Everyone else needs training. Books are great and portable. CM is probably a little more efficient beause of the feedback and the always available diagrams. Don't be afraid to review the courses to get continuing feedback on how much "stuck".
I'm still a novice at chess and was wondering if I should be foucsing more of my efforts on the Tactics Trainer or Chess Mentor. I'm fairing much better on the CM and my raiting on TT is horrible, even though I've only recently started. Ideally I could use both but I don't have the time right now.