A while back someone suggested this (Mitthrawnoruodo, IIRC) and now it's the first thing I do when I get onto macrumors.
Replace the "YOU" with your username and bookmark the URL (
NOT the search result)
Code:
https://forums.macrumors.com/search/?do=process&starteronly=0&searchuser=YOU&exactname=1
It searches every thread you've ever posted in and gives the results back in chronological order to recent posts.