Have ever removed and serviced those Nissin calipers Ryan, they do need a service every now and again because some of those pistons love to get stuck. Those calipers are far better than most guys will tell you mate.
You can do it yourself Ryan, all you need is some brake cleaner and new brakefluid. It's been well documented in the past and I recently did a friends on his bike. The middle 2 pistons I think where the one's getting stuck.I haven't had them rebuilt or anything, just flushed a couple of times. Do they need to be redone that early? I've just ticked over 11k. They dont really feel different to when I first got the bike with 352 miles on the clock (but 10 years old), just got spoiled with the setup on the Guzzi.
I figured I could be fine with those calipers since fade isn't a real issue for me. I was first hoping I could get more bite with a different pad material.