Donncha, how many sites do you have that use the same set of files?

I maintain multiple sites on one set of WordPress files (see my experience here) and I find upgrading anything, even a plugin, to be a lot of work because I have to visit every site, disable plugins, upgrade, then visit each site again to enable plugins.

Do you have a different procedure? How do you upgrade quickly when using the same set of files?

Thanks,
David