There have been quite a few upgrades since version 9. However, to take advantage, you would have to open the application in the development software, add the items that use the new features, create a new runtime, and then load that runtime into the PV.
If you aren't doing any of that, then there really isn't a *need* to upgrade. But I agree with the other comments about upgrading all my PVs to keep them all at the same version.
I suspect a case could be made that for security purposes, keeping them all at the latest version is more secure. I know that is probably debatable though.
OG