I check all pistol and revolver brass for maximum length, and set aside those that need trimming.
I assemble nearly all revolver ammo with cast lead bullet that have a crimping groove in the design. Case length is critical for crimping into this groove.
I check all semi-auto pistol cases for maximum length, then set aside those that require trimming. In my experience, the 9mm Luger is the worst offender, especially if the cases are of foreign manufacture.
The .45 ACP rarely requires trimming. Once in a great while I find a single case out of hundreds that's a little long.
On revolvers, the .357 Magnum seems to require the most trimming, I've found. I shoot almost exclusively lead bullets, requiring a roll crimp into the groove.
Interestingly, the worst offenders I've found for being overly long are factory-new, unfired .30-30 and .32 Winchester Special brass. One of my older Speer reloading books cautions shooters to watch for empty .32 WS brass being too long.
I size all brass, even new unfired stuff, before loading and then check case length for trimming -- handgun and rifle brass. I never assume that the factory got it right. If you've ever been in a munitions plant, and see how quickly brass disks are made into cases, you too would wonder how in the devil we get such uniform cases from such mayhem.
But we do. Nonetheless, there's a margin of error in everything, even nature -- they're called
mutations.
I've been reloading for nearly 40 years. I check brass length religiously, and trim as needed. Others may consider it a waste of time with handgun brass, but it makes me feel safer about my reloads.
Whether it makes for more accurate ammo is probably moot: these 54-year-old eyes ain't what they used to be. Time was, I could spot a pretty woman in a blue dress at 200 yards. Today, I'm more inclined to see a mailbox at 50 yards, squint, and think she needs to go on a diet!