I have the Medela Pump in Style. I started using it once a day at 6 weeks and now use it every day (more on 3 days I work). I have on order a set of new tubing and the little rubber pieces.
How often do you all replace them and do you find it impacts output to do so?
Re: How often do you replace pump parts (and which)
You shouldn't have to replace tubing unless milk gets in them, or if you let moisture sit in the tubes. You are supposed to let the pump run for a couple of minutes after you finish to clear out any moisture that accumulated in them. Replacing the tubing will not help output in any way, it only makes it more sanitary if there is anything in the tubes.
I replace my membranes every month or so, after 60-70 pumps. My output doesn't really change, but the amount of time I have to pump to get the same amount does. They get worn out and get more flexible as time goes on, and I find that the better suction decreases my pumping time with new membranes.
You don't need to replace anything else, although periodically sterilizing everything but the tubing is good practice. You shouldn't need to sterilize the tubing unless you got milk in them.
Call their customer service. I have only ever heard great things! They will get you a new pump ASAP if they can't troubleshoot it over the phone.