I'm using splunk free license cause i don't need more then 500 MB per day, but it show that next month this free license will expire , how to avoid that from happen ?
It looks to me as if that's the expiry of the Enterprise Download Trial license after 60 days. You can convert that to a perpetual free license at any time.
Free license cannot expire. Check "all licensing details" at debug information in licensing.
At the forwarder you will see a date in the far future. (2030+). That is because the forwarder is in the free license. The trial license however expires in 60 days.
It looks to me as if that's the expiry of the Enterprise Download Trial license after 60 days. You can convert that to a perpetual free license at any time.