It takes more than a month.
Can't progress

You need to be very quick on your moves because the penalty for being slow is harsh. I doubt that I would be able to get much above 1600 as I am rather slow in working out solutions.. You can even lose points for a correct solution if you are too slow.

@8130858 at least 2 moves. Can't calculate more than this if I am in a hurry (which is always the case).

@owltuna you just contradicted some of this topic and doens't explain why and how I need to not be in a hurry. Could you explain better, please?

I agree with owituna, so why are you in a hurry? If its the timer on the tactics then i would just ignore that, hopefully speed will improve as you practice the calculations.

Many times I tell newbies this:
Tactics is not about speed. It is about accuracy. Ignore the timer. Ignore your TT rating. Just get the tactic RIGHT, not matter how long it takes you.
Eventually, you will get faster and faster at doing the problems and your rating will climb as a result.
Anyone who says that speed is important at your level is giving you bad advice. Ignore them as well.
BorgQueen is right--resistence is futile!

Many times I tell newbies this:
Tactics is not about speed. It is about accuracy. Ignore the timer. Ignore your TT rating. Just get the tactic RIGHT, not matter how long it takes you.
Eventually, you will get faster and faster at doing the problems and your rating will climb as a result.
Anyone who says that speed is important at your level is giving you bad advice. Ignore them as well.
I almost agree.
But the "at your level" in the second from last sentence is too much.

I've been stuck at 2300-2400 for about a month now, and before that I was stuck at 2000-2300 for about half a year, with little progress. Of course, tactics trainer ratings are not exactly accurate with your real playing strength.
I'm been training tactics at a regular basis for about a month, but I can't progress any further than 1450 rating tactics. Can someone give me a hint on how to get better at tactics?