my first couldn't nurse so I pumped. I pumped for 6 1/2 months, and then fed milk from the freezer for 2 more months. That milk that she was getting at 7 and 8 months was produced when she was a newborn-6 months. It was perfectly fine. While the composition of milk does change, it is still great for baby- even milk from a different time and frozen still has more beneficial properties than formula.
This little one will be getting frozen milk when I quit pumping. I don't see an end in sight, so she may be over 1 and getting frozen milk!
You need to pump if you're not going to breastfeed, if you skip pumping your body will think you don't need as much milk and won't produce as much. The more you feed and the more you pump the more your body will supply. So make sure if you're not feeding, you are pumping. Either way is fine.
It's YOUR body that regulates the milk. That's why many lactation consults say that if you can't nurse for whatever reason you can pump and feed.
I'm a working mom, so I need to pump, DH stays at home with our son (and future child). I agree it's nice to have some milk on hand if you need it.
From what I read it's not THAT big of a deal, it's most important in the early weeks as that milk is more fatty. If you pump to store for when you need it that won't cause any issues with breastfeeding. Just make sure your child doesn't get more than one (or maybe two) bottles at a time, they may reject the boob then (as my son did).
Due to my son refusing to nurse and biting me I pumped exclusively for several months, my son never really got sick, and grew just fine. In fact he ate SO much were not sure where he puts most of it because he's below weight, yet has always eater much more than a baby his age should. Just because I pumped, my milk was just as good as if he was feeding from me, so you should be more than fine pumping a little here and there.