How long can nipple clamp be worn safely?

I’m wondering about the safe duration for wearing nipple clamps. I keep mine on for hours, tightly secured and painful, which is all part of it. Once I take them off, that removal hurts too, leaving my nipples sore and tender for a day or more afterward. Is there any real risk of damage from this? I figure women need to be careful not to hurt their milk ducts. Men don’t have that specific concern, but is there still some risk involved? There doesn’t seem to be much discussion on the topic here yet. Any thoughts would be great.