Sure, that's a valid perspective too. Yes, if you use your own domain for email and fail to renew the domain for any reason, someone can take it over your email address too. One more reason not to use custom email domains.
I just figure that if I have a choice between an email provider that will let me keep my email address for the rest of my life and never give it to someone else or one that will give my email away not very long after I stop paying, I'm going to go with the longer-term, more stable solution. Like you said, there are no guarantees in life and life is short, but why make things more risky and complicated for myself?