My comment was more a general statement to combat a type of procrastination (a deadline which must be met slightly before its date), specifically with the mechanic of both automated and manual subscriptions. Calendar reminders work wonderful with _both_.

I can also think of various scenarios where you don't want certificates to be renewed. Or well, maybe you don't but the users would. Like for example when your server no longer works, or got confiscated. A low timeout aids in lowering the amount of those certificates.