SIM card usage - How to switch SIM card every 4 hours?

In the configuration tool go to Gateway configuration GSM outgoing groups and Set Mode of switching SIM card to Random. Then go to Time limits and set time interval Time limitation from 03:59 to 04:01. This time interval has to be set for all inserted SIM cards (SIM 1 - SIM x).
With such a configuration 3:59 is minimal interval for switching SIM card and 4:01 is maximal interval for switching SIM card. Thanks to this settings SIM cards will be switched approximately every four hours.