I've always heard breastfeeding hurts. I might let him try it a few times, but making it a regular event would be kinda silly. I do get tired of guys insisting on doing sexual things over and over that are sheerly for their own pleasure and make us physically uncomfortable.
That only happens if a woman is lactating, because she is either pregnant or breastfeeding a child. I am not either of those, but I find it very arousing when a man sucks on or licks my nipples and breasts.