A customer can exit the browser or leave the catalog pages at any time, and no indication is given to the web server aside from the lack of further requests that have the same session ID. Old session information needs to be periodically expired. The SessionExpire specifies the minimum time to keep track of session information. Defaults to one day. Format is an integer number, followed by s(econds), m(inutes), h(ours), d(ays), or w(eeks).
SessionExpire 20 minutes
If CookieLogin is in use, this can be a small value. If the customer's browser has the Interchange session cookie stored, he/she will be automatically logged back in with the next request. Note, however, that the customer's cart and session values will be reset.