I've had my nips pierced at 4mm/6ga for ten years. Putting in the second jewelry was the part which stung the most, but it's quick and done. Get them both done at the same time. Being told not to touch them for six weeks is tough when you just want to play with them. I always had sensitive nips, but the piercings took it up a couple steps for pleasure. Most guys like them. A few won't touch them. Some will nurse on them until they're raw. They will feel better as you stretch to larger gauges, more sturdy, and less vulnerable. I change jewelry once in a while, but keep going back to seamless segment rings because they are the most comfortable and easiest to keep clean.