Looking at the relevant limit, "Consecutive Authorization Failures per Hostname per Account"[0], it looks like there's no way to hit that specific limit if you only run once per day.
Ah, to think how many cronjobs are out there running certbot on * * * * *!
[0]: https://letsencrypt.org/docs/rate-limits/#consecutive-author...
I hope they don't go any shorter than a month. Let the user pick, any value up to a year should do.
Incidentally the fact that it took them 4 days to respond to that issue is why I'll be wary of getting 6-day certs for them. The only reason it wasn't a problem there was that it was a 30d cert and had plenty of time remaining, so I was in no rush. (Also ideally they'd have a better support channel than an open forum where an idiot "Community Leader" who doesn't know what he's talking about wastes your time, as happened in that thread.)
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.
(90 days will remain the default though)
SES? Around $0.0001 per e-mail
For a free service, that's a whole lot of money.
It's very under-engineered, maybe a trifold pamphlet on light A11 printed with a laser jet running out of ink.
I've probably spent more time talking about how much it sucks than I have bothered considering a proper solution, at this point.
I respect this. Reading someone else write this makes me feel more comfortable thinking about the things in my life I could be doing more to improve, which makes me respect this even more.