How quickly must I be able to replace a certificate?

As detailed in the Google Trust Services (GTS) Certification Practice Statement and Subscriber Agreement, GTS may need to revoke or opt to revoke for a number of reasons. Subscribers must be able to rotate certificates quickly should revocation be necessary. To prepare for revocation that may need to happen within a tight time interval, it is strongly suggested that subscribers use an ACME client with ACME Renewal Information (ARI) support and configure certificates such that they have fully automated lifecycle management. There are circumstances where Google may need to revoke within 24 hours or 5 days, even if doing so would cause adverse impact to a subscriber.