A site audit reports twelve hundred title tags over the display limit. You are not rewriting twelve hundred titles, so the question is which ones matter.
Sort by severity, then by traffic
Longest first tells you which titles are worst affected. A title thirty characters over is losing far more of its message than one three characters over. Cross that against the traffic each page receives and the top fifty are obvious.
What the extreme cases usually reveal
Titles at the very top are rarely just long — they are usually a template bug, where a category name, a site name and a product name all concatenate. Fixing the template fixes hundreds of pages at once.
Diminishing returns are real
Pages barely over the limit lose a word or two of a title that still communicates its point. That is worth fixing eventually and never worth fixing first.
Try it: Sort by Length (Longest First) on SeoWolf's Notepad.