Campaign links are only as good as the tracking on them, and tracking is only useful if it is identical across every link in the campaign. One mistyped parameter and that click lands in a bucket nobody looks at.
The realistic failure
Someone builds forty campaign URLs by hand over two days. Thirty-eight carry utmcampaign=spring-launch. Two carry springlaunch and springlaunch. In the report, the campaign appears to have three separate identities, none of which show the real number.
Doing it in one pass instead
Paste the forty destination URLs, append the full UTM string once, and every link in the campaign is now provably identical from the ? onward. There is no version of that pass that produces two spellings.
Check before you ship
Run the finished list past a duplicate check. If any two lines match exactly, you have pasted the same destination twice — which is worth catching before the links go into an email that cannot be recalled.
Try it: Add Suffix on SeoWolf's Notepad.