Every ad platform truncates headlines past a limit, and it does so silently. The ad still runs. It just runs with the end of your message cut off, and nothing in the interface tells you which of your ninety variants are affected.
Measuring the whole set at once
Paste the headline list, append the character count to each line, and the overruns are immediately visible. Sorting by that count puts every variant at risk at the top of the list, in order of severity.
Why the limit is not the real threshold
Aim comfortably under the maximum rather than exactly at it. Platforms differ on whether they count spaces and punctuation the way you do, and a headline sitting one character under the documented cap is one dynamic keyword insertion away from being cut anyway.
The same check, other places
Meta descriptions before a bulk upload, subject lines before a send, push notification bodies before a schedule. Anywhere text meets a hard limit, measuring the full set beats spot-checking a few.
Try it: Append Character Count per Line on SeoWolf's Notepad.