Periodically upgrading your Kentico Xperience site to the latest version is usually a good idea. You'll be able to take advantage of all the latest features, security updates, and performance improvements that have been released since your site was last updated.
It is important to remember, as well, that Kentico will only provide technical support for the most recent version of Kentico Xperience and for two versions behind (e.g. if the most recent version is 13 then 13, 12, and 11 are the supported versions).
Upgrading is a relatively complex task and should only be done by an experience Kentico Xperience developer. If you would like help upgrading your site or even weighing the benefits and deciding whether an upgrade is right for you don't hesitate to reach out to the Toolkit For Kentico team.