Changing out paci's

Dawn
How often do you change out your babies paci's from day to day? I usually try to switch them out daily so he gets a fresh clean one each day. 
But also, how often do you throw your paci's away and replace with new ones? We have several Nuk paci's we use and change out daily and when I am washing them I have started to notice the nipple part starts to look cloudy in color instead of clear when we first got it. And also, if I look close, right around the base of the nipple, there is often times build up of gunk and I have to use my fingernail to get out, such a fuzz, dust, etc. 
I was just curious how long people typically use a paci for before pitching it and getting a new one because that one is gross.