This begs the question: if I could remember to renew the cert 365 days before it lapsed then I could as easily remember to renew it 45 days ahead (which, operat

This begs the question: if I could remember to renew the cert 365 days before it lapsed then I could as easily remember to renew it 45 days ahead (which, operationally speaking, is as good). In any case, certificates can only be purchased for a one year term now, so your hypothetical "one year ahead" doesn't fit the problem. Even if buying any updated cert that far ahead creates the same validity period it's not the buying the cert that's the catch — it's the deployment of said cert.