Trims

I wouldn't go to that hairdresser.  To a hairdresser, the word "trim"  means "remove the ends of the hair to a point above where it looks dry or split, or to the thickest point".  And to a hairdresser, this point is often 1 to several inches up the hair, even on hair that looks completely healthy to the average joe.  So saying the word "trim" to a hairdresser is often one mistake longhairs make.  A trim to your hair is whatever you want it to be, even if its only 3 milimeters.   

PurpleBubba....you NEVER sound preachy! Your advice is excellent

A trim is whatever you say is allowed to be trimmed.

I've seen lengths under an inch called microtrims but that might not be a term stylists know.

It does not matter whether a stylist or anyone else is nagging you. It is always your decision how much gets taken off. And if they do more than that without your permission then you don't pay, tip, or return to them.

It doesn't matter whether the person has been your stylist for 20 years or never before. You get to decide period.

Now having said all that, do not just say trim it. Give a specific length. If you have to bring a tape measure or ruler you are within your rights to do so. I've seen stylists posting on forums that they have had clients bring rulers.

Another thing is the first cut. The first cut of a trim is going to be the guideline for how long the rest will be. That's because you match each consecutive section to that original guide length. So tell the stylist that you want to see the hair that is cut in that first snip. A good stylist should show you that anyway.

Remember you can always go back for another small trim when you feel that you need it.

Good luck. I hope I didn't sound too preachy.