Count every post with code
Two posts failed on X after small edits pushed them over 280 characters.

Note
Notes are where things go before they turn into a case study. Some never do, and that’s fine.
X allows 280 characters on my account. Two posts failed to publish after small edits, a name here and a price there, pushed them over.
Now a script counts every post before it's scheduled, and again after every edit. Links count as 23 characters, whatever their length.
Eyeballing a character count is how you end up apologizing to your own schedule.