To be honest, if you are looking at expressing long term I would be going for the *good stuff*. If you want to buy, a Medela freestyle would be the best option. The Ameda purely yours is good too. I don't think the medela swing will cut it for really long term expressing.
Have a look at the Australian Breastfeeding Association's online store, Mothers direct. They offer 10% discount for members - it's a significant saving on a good breastpump.