Sylvain,
The 'max-timeout-flush-interval' configuration entry is still available, it is just that it has not been documented. The way that the session cache works is that a thread periodically polls the cache for expired entries – and max-timeout-flush-interval can control how often the cache is polled. This thread is purely used to reduce the size of the cache, and is just one mechanism by which expired entries are removed. If a request comes into WebSEAL for a particular session, a check is also done at this point in time to ensure that the session has not expired.
I hope that this helps.
Scott A. Exton
Senior Software Engineer
Chief Programmer - IBM Security Verify Access
IBM Master Inventor