Couple of options are there.
--> Increase your Cache directory size
--> Increase the Cache size in Session properties.
--> You can build a small pre-processing command to cleanup the Cache directory provided this activity doesn't impact other workflows. (Just to automate whatever you are doing manually)
--> Hope you've gone throw below discussions as well. If not, please go through.
With all due respect I fear that this is the wrong approach. We should not focus on remedying any symptoms, we should look for "clean" solutions.
First you should find out WHY those sessions create such (obviously) huge cache files that they fill up the cache directory.
Often mapping logic can (and should, from a performance perspective) be changed in order to considerably decrease the amount of cache files and their sizes.
But again, this requires some more thorough analysis. May I suggest that you hire someone experienced in such analysis if your team doesn't have anyone who can do it. Some changes in the mapping logic and/or the overall process designs might well be appropriate.