[TimWolla]

> I believe most clients renew certs ~10 days in advance.

The recommendation and the time certbot uses is 30 days.

[tehbeard]

I've heard 10 days before, possibly older documentation?

[Arnavion]

Based on the reminder emails they've sent me, they recommend renewing when one-third of the current cert's validity is remaining. That is, 1 month for their 3-month certs.