ExpiredLeaseTimeout defines a time value in seconds.

ExpiredLeaseTimeout=4294967  ; Approx. 49 days

The mechanism that checks expired leases is triggered by this. Regardless of when the next lease expires, the mechanism is scheduled at least in the time interval specified by ExpiredLeaseTimeout. This is useful when the INI file entries get changed manually and the DHCP server may not be aware of already expired leases. By this, the INI file gets cleaned up cyclically.