This defines the maximum amount of time that a client (browser) is allowed to remain connected to the cache process. This is merely a safeguard against clients that disappear without properly shutting down. It is designed to prevent a large number of sockets from being tied up in a CLOSE_WAIT state. The default for this option is 1440 minutes, or 1 day.
The default value is intended to be much larger than any client would ever need to be connected to your cache. You should probably change client_lifetime only as a last resort. If you seem to have many client connections tying up file descriptors, we recommend first tuning the read_timeout, request_timeout, pconn_timeout and quick_abort values. If the more file descriptors are in use then the memory in use will also increase, which is also a performance issue.
Client lifetime with the cache
client_lifetime 1000 minutes