You may run into a Kernel Panic. Then your are hosed and may have to start all
over again.

Well that sounded helpful... The simple answer is, yes. He you install
a kernel update you custom kernel is not lost but will usually not
boot to it by default. When an update comes out, get the source and
build that then install the new custom kernel. If I was at home, I
would send you a link to building a package with your custom kernel in
it. I am not though, Google 'kernel ubuntu way' should give something
helpful for you.

Rebuilding kernel isn't something I want to do
each time an update/patch/distro upgrade comes along,
so I'm reconsidering the whole "let me see if it helps"
outlook.

Maybe one day, when I have a lot more free time on my hands....

You could see if one of the other Ubuntu kernels helps, it has multiple
builds. Usually the installer picks the best one, but not always.

And it is not any time ANY update comes out, just a new kernel comes out,
which isn't all that often.