Since this thread has 893 views, and 0 replies, I'll post my own reply.
During more than 1 year of using LiveCycle, the only way we have found to prevent LiveCycle from filling up our temp drive with A3DRCache data is to manually delete the contents of that directory (or to use a script).
Most conversions do not leave data in this directory, however it appears that if a conversion times out without completing, or runs out of memory, (as frequently happens with Large CATIA V5 assemblies) the Cache data is left behind.
This is my best guess, but I have not confirmed it.
I hope this information is helpful!