I was so concerned about this a few weeks back and asked nearly everyone I came into contact with taking particular notes from the childhood nurse...(silly me)
I had responses such as the dummy needs to be sterilised directly before giving it to your baby (which is alittle hard when you have to distract a baby for 20mins while the electrical steriliser or 4 mins while the microwave steriliser do their jobs and even worse if you use Milton which takes 1 hour to sterilise!
I was told that if you let them air dry, bacteria walk along and attach themselves to the equipment. The best advice in relation to this type of question, is best answered by friends as the professionals need to tell you what they have been trained.
I agree with what has been posted already ... sterilise once at night unless it hits the floor...then depending on how dirty the floor is either run under cold water (hot water tank has alot of dirt buildup unless brand spanker) or resterilise.
Daniella, Sydney, 15 month old