You might get a lot of different answers on this. My answer would be, accuracy is much more important than simply rushing through the problem.
A lot of people completely misunderstand the concept of "pattern recognition" and think that spending 2-3 seconds on every problem, getting around 45% of them wrong, still improves your tactical ability since you're seeing "many different patterns." I think that's complete nonsense.
In my online tactics training (not on this site), I try to keep the accuracy level at 90% (that is, I try to get 1 wrong problem maximum for every 10), and try to spend whatever time that takes to reach that percentage.
I have been enjoying Tactics training and have a quesiton about speed for advanced players.
At the tactics training, I can solve most all of them, but not within the time frame to increase ratings points.
How important is speed in improving overall chess play?
At the chess tactics server, I can't break 1400 as I solve, but lose .2 for example, due to time elapsed.
How valuable is this training once the patterns are recognized?
thanks