Hi. I just bought an Avent Isis hand pump (which is great!), and the instructions say to wash with soap and hot water AND sterilize after each use. I've previously been using the Medela Harmony, and I just wash with soap and hot water each time, only sterilizing before the first use. I don't have a sterilizer and it seems really excessive (and impractical) to boil all the pump parts for 10 minutes each time I use it. Is this really necessary, or a ploy to urge you to buy their sterilizer? Any tips on how often to sterilize?