I use the Lee trimmers too, new brass is very inconsistent in length, I've not loaded for the .223 yet, but many other calibers there's always some shorter brass in the bunch, to add a little consistency to my load work, I like all my brass to start out the same length, so I find the shortest of the batch, shorten the pin end of the case length gauge just enought to clean up the shortest round and trim all rounds to that length. I don't think it makes any difference if they're a touch short, but it sure makes a big difference when I crimp which I do to all my ammo. After all, accuracy comes from consistency between shots, the less variables there are, the more accurate the ammo. Works for me!!
I've read of the pin end of the case length gauge wearing down and/or a hole wearing in the lock stud, but I haven't experienced that......yet!!
Tim