Timezones going to make that hilarious, probably go back to much longer certs. I like free so I put up with LE. The automated stuff only works on half my servers, the other half I either run without https or I manually install it. Except now I wait until the service stops working, spend 15 minutes debugging why, go to the domain in a browser and see the warning, and then go fix it. Why? LE decided sending 4 emails a year is too many. And let's be real, sending automated emails is expensive. I think AWS charges like $0.50 per email when you use their hosted email sender.

They simultaneously want shorter certs but can't cope with the current load

That's a good point. I suspect as the renewal period is shortened, scripts will attempt renewal faster and faster.

I hope they don't go any shorter than a month. Let the user pick, any value up to a year should do.

No, they will never get that short due to reliability issues. I could see getting down to maybe two weeks.

To make 24 hour valid certs practical you would need to generate them ahead of time and locally switch them out. This would be a lot more reliable if systems supported two certs with 50% overlapping validity periods at the same time.