I trim to 1.75 after every firing. 1000 brass might only take me an hour and a half, so I do it every time. Most if not all of the brass is still well within saami spec but it would be my luck I get one thats grown too much and I have a jam or worse during a match. I figure with as much time, effort and $$ it takes to shoot accurately, I might as well not take any shortcuts.
Can you get away with not trimming every time. Most definitely. I am just too ocd lol.