You are being downvoted, but it is a reasonable question. If you can renew every 45 days, why not every, say, 3 days?
OSCP stapling except without the oscp stapling part.
OSCP stapling except without the oscp stapling part.
Instead, I would surmise this is the first step in that process by introducing a window short enough to act as a forcing function on automating certificate issuance & renewal. It's short enough to strongly encourage leveraging automation everywhere possible, but not so short that one could argue it's impossible to do manually for things that still just can't do this automatically, of which there are still a disappointingly significant number.
Once we begin to get below 30 days, however, I suspect there will be a lot more scrutiny around the data suggesting exactly how small a window is sufficient. From a risk standpoint, if we're arguing shorter-is-better, then we should go as short as possible: someone will need to pull together the data that suggest exactly how small a window appropriately balances the various risks involved. (And then 15 others will need to argue about the validity of the data, whether the data actually suggest that, whether the data were assembled with an agenda in mind, etc., etc., etc.).