I never see any hot pixels with the 20-30" exposures, regardless of ISO. With the foreground exposures though, there are quite a few- but nowhere near as bad as the canon 6d I had, which looked like confetti cake when zoomed into 100%. I don't use long exposure noise reduction, but I do take a dark frame with my lens cap on that matches the longest exposure I took over the course of the night, and then use pixel fixer in post. I usually just take the dark frame as I'm packing up the rest of my gear to go home once I'm done shooting. Easier to do that than wait an extra 8 minutes or whatever each time I take a long exposure, especially if I'm doing things like focus stack my foreground exposures
Oh...now you see. I NEVER think of taking a dark frame. Is pixel fixer a download software program?