multiple apps using same IWCACHE folder

Should I set each ISAPI IW apps's cache folder to a unique location. I have 4 IW apps all using the same location "C:\IWCACHE" and have noticed that there are a number of cache folders that are many days old. I am not sure if it because the App pool is timing out thus killing the IW app or a conflict with multiple apps writing to the same cache folder location.
My understanding is that the cache folders are deleted after several minutes past session timeout.