If you're manually installing them outside of Ubuntu package management then you need to reinstall them every time you upgrade your kernel. (This is a design decision by Linux to make life harder for closed source drivers, there's nothing Nvidia can do about it)
If you're manually installing them outside of Ubuntu package management then you need to reinstall them every time you upgrade your kernel. (This is a design decision by Linux to make life harder for closed source drivers, there's nothing Nvidia can do about it)