Ok, my answer is a bit different. Sorry if you find this gross, but as I pumped everyday at work (3-5 times a day), I had to be realistic. I didn't wash between daily pumpings. I figured that bm was sanitary and if bottled bm could last 10 hours at room temperature, then my pump was not going to be exposed to "bad" milk. I washed the pump every evening in hot soapy water and let it air dry. I would sterilize only once on the weekends generally. My minimal approach never seemed to cause any problems.... HTH.