Please check this 100% crop of a night sky.
I shot this on a Nikon D750 with a Nikkor 50mm f/1.4 D @ f/8, ISO 100, RAW format.
I had already noticed that kind of noise / hot pixels (all these small RGB dots) on much longer shots, anywhere above 10-15 minutes. But this shot was only 269 seconds (less than 5 minutes).
Is this a sign that my sensor is slowly dying? And is there anything I could do to prevent this to happen aside from turning on the long exposure noise reduction?