nipple size change/replacement parts

So I’m getting ready to buy a breast pump but I am trying to get everything at once because I have to use a third party company to get my pump delivered to Canada and it’s quite the process. So I’m trying to get one big shipment.

2 questions

1. Does your nipple size change from pregnancy to pp? Like can I measure myself now for some flange sizing or does it all change??

2. What parts should I expect to change on a spectra s2? This is what their website says. So I was planning on buying some extra parts to have on hand throughout the year.