Appendix C: Support Information : Software support policy
 
Software support policy
This Software Support Policy applies to any and all software produced and / or sold by Fortinet, covering firmware for appliances and applications (Software) installed on customer owned systems.
Fortinet will provide Software support for thirty six (36) months from the GA release date of the major or minor release. Software Releases constitute either major or minor version increments and support is provided on the latest patch release of each version.
Although a firmware or software release may be currently supported for customer service & support, it may not be supported by the firmware release of another device. Review the Product Information and Support chapter of the firmware release notes for a list of supported devices and firmware releases prior to upgrading your device.