Im down to 6/32 all 4. The tires are only 300 treadwear.
That's still a bit of tread. Sounds more like you want to replace just to replace and not out of need.
I drive used tires, extensively. But tests show that new tires give the best braking, handling, & resistance to hydroplaning. Its easy to see why some people like to buy new tires, even when their old tires are well above the wear bars.
I noticed on a trip in the rain the other day the front was a lot lighter than it should have been. The tires are still safe, but not up to my standards. I will wait until they get down to 3-4/32 though just because. I only bought the thing a few months ago back in late February, and I want a bit more bang for my buck with these tires, lol!