Who are all these Keiths in their 40s??? I'm in my 40s. I never went to school with a single Keith or knew one my own age. They are all my parents' generation -60s, 70s, 80s.
I do think Keith Richard first, which is not a bad association I guess. Although someone else's description of Keith drinking real ale, having recently retired from s job in health & safety seems fairly apt. He probably wears dad jumpers too. The name itself isn't awful but I think it might need another decade or two before it's ready for a comeback.
There is a little Brian at out primary school. That surprised me.