Uptime complacency?

I have a fan-less BSD 10.2 Server running MySQL 5.6 I put in for a factory system and which has now been up for just over 300 days since it was built.

It is running along nicely and nobody is complaining but I am starting to get worried I should be doing some preventative maintenance other than the usual resource utilisation and backup checks or even just do a restart just for the hell of it! (Note I am not a *nix guy but the BSD/ZFS system came highly recommended and the build instructions seemed full proof but 300 days seems a lot for a windows guy)

I wont go into specifics but in general what are good things to look out for or check for me and other people in a situation such as this where you could get very complacent?