you "have" to wear your nursing bra twenty-four hours a day because if you
don't, your breasts will sag! or at least that's why this advice is given out.
and of course you wouldn't want anything gross like breastmilk leaking out in
the bed, would you?

i had a client who had mastitis so awful she was hospitalized, and then it was
still not going away at six weeks, and when i saw her in her bra, i could
instantly see why. it was too tight, and yes, she wore it 24 hours a day as
she had been told. she was told that a "supportive" bra was best, but she
interpreted that as meaning tight.

carol brussel IBCLC

"if it feels good do it" - like not wearing a bra to bed if you don't want to