unless it fails to clear the stuff swapped onto the hard disc each session so that it accumulates. Is that possible? Then would Crapcleaner clear it all out once a month or so, when I get my hands on it?
In a word, no.
Without knowing what "crap" "crapcleaner" is "cleaning", it's all speculation.
I suspect that it is all down to temporary internet files and browser cache.
Another possibility is something doing very verbose logging - I've seen servers with 3/4 million log files filling the system disk - but unlikely on a home PC.
Tell us what CC is set to do, and then maybe try it with only one option ticked, then 2 etc. until you see what process reclaimed a humungous wodge of disk space (that's a technical IT term, btw).
SD