I'm going to try contacting Medela and see what they say and I'll report back. When I was originally pumping for my daughter (2 years ago) thats what customer service had told me when I called. I remember being shocked! I can't find anything written to support what I was told so I'll see if they still stand by that guideline of 4-6 weeks. My impression (not that I've been told) is that they "wear down" with very frequent use, such as exclusive pumping.
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