The current plan is for the floor to be 47 days. https://www.digicert.com/blog/tls-certificate-lifetimes-will-officially-reduce-to-47-days, and this is not until 2029 in order to give people sufficient time to adjust. Of course, individual certificate authorities can choose to have lower validity periods than 47 days if they want to.
Essentially, the goal is for everyone to automatically renew the certificates once per month, but include some buffer time in case of issues.