For DHs shirts I send them out to be laundered and pressed so just 1 wear.
For me, tops generally 1 wear because of babysick but agree if it is a top worn on top of another top, I will put it back in the wardrobe.
Anything silk goes to be dry cleaned at same place as DHs shirts, so they are worn once then put to one side for cleaning.
Undies just 1 wash and sometimes, if I am going out, 2 pairs a day (or if I shower in middle of day, new pair on)
Jeans though I wear for ages (rotate between skinnies, wide legged, boyfriend, normal bootleg) but the minute any babysick on them that is not baby-wipe-able off, they are in the wash (and now we are giving solids, that carrot does stain!)
Bras every few days but does depend on what top Iam wearing.
Do use fabric softener (comfort creme) but do not tumble dry, always air dry.