After determining the max and min OAL, I pick the middle as a length by which I measure.
Using my (good-quality) caliper, I quickly sort through sized cases, culling into two piles, those that are above the mid-length (which are the ones to be trimmed) and those that are below the mid-length which won't be trimmed.
I can go through 1,000 cases in less than about an hour.
I then set up my Forster (hand-crank) trimmer for the Trim-to length (minimum length) and trim all the culled cases that are now in a pile that are all over the mid-length.
I would say, doing this in several sessions, not all at once, the total length of time for 1,000 cases would be about two to three hours, maximum.
When reloading, any part of the process that is handling and performing the same task many times over, I find I get extremely fast at each of those tasks. Of course, I need to give my hands and body a break, so I stop every so often to go get a large drink of water, get the mail, check email, etc.
I am typically not in any hurry, whatsoever, when reloading, so it may actually take me days or weeks to finish such a task, doing it when I'm in the mood and when my body is working well and up for it.