Recaching interval not long enough on slower systems

[conaticus]

The interval works well on most systems, but slower systems or systems with a bigger file system have the chance of not being able to recache in time for this 30s interval.

The best solution is to have a check to ensure that the previous recache is completed, and skip if it is not. We could implement an algorithm to check for file changes first, but these usually happen so often that it would be redundant.