I have NEVER trimmed a straight-walled pistol round. Never will. Don't see it as necessary. By the time they've stretched to the point they need it, they're starting to split, and the primer pockets are getting loose. In the case of the 45ACP, they tend to shorten over time and usage.

My Lee trimmers are factory-set to the "trim-to" length, which always seems to be 0.01" below the maximum allowable length. Most are right, but a few have needed to be adjusted a bit.

The bottlenecked rounds tend to grow longer with each firing, which happens faster with full-power loads. If you trim to the recommended "short" length, you should get about five firings before they need trimming again. A well-known ballistic expert, whose initials were Ed Matunas, used to say that after a fifth trimming, the cases were ready for the scrap heap. I have yet to see a case that lived long enough to need TWO trimmings, let alone five.

But of course, your results may be different.