If your configuration directory is not /var/imap, adjust accordingly.
Given the potential load, this is a good candidate to move elsewhere. This can be done by symlink'ing the directory to another partition. We symlink it to a directory on a memory/viritual memory filesystem (specifically Solaris' tmpfs). If you use a tmpfs type filesystem, make sure that you have sufficient memory/swap to do this.
Some people don't care about this information and just #ifdef out the code. We probably should add a configure option to do this.
We run with it enabled and it doesn't significantly impact our performance.