Hmya, this is a bit like worrying if you have a good backup in case a meteor impact destroys the machine. The user of your shell extension would have figured out a while ago that something is a-miss. Getting 100+ DLLs injected into a process every time he uses the File + Open dialog does not go unobserved, that program is dead to the world for a good 5 seconds or more.
So either he does something about it and cleans up his machine with a utility like SysInternals' AutoRuns. You'll survive that if your extension is useful enough. Or the user takes no countermeasure and is happy that there's a hard upper limit. Your extension will fail but there's no way for the user to tell why. You might get a support call, you know what to do about it.