hopefully never again. I'll never forget what my nurse said to me. She said she had 4 children and had passed a kidney stone one time. She said she would rather go thru childbirth 4 times again than to pass another kidney stone.
If your husband is worried about the final stage (i.e., the stone passing thru his you know what), tell him that's the easy part. Almost no pain there. It's the stone passing from the kidney to the bladder that causing the pain. And if it helps soothe his concerns, I've also been told by some people that even that stage did not hurt them all that much.
And of course it depends on the size of the stone too.