W0506 are the bushes you want - they are the front lower control arm bushes, and the ones that wear out the quickest. While you are there it's often a good ideal to also upgrade KCA334 which will help as mentioned.
The poly bushes don't wear out faster than the stock bushes - that's part of the point. They have much less give than the standard bushing, so make the ride a slight bit harsher - the difference here isn't huge though.
This is the link you want for all the whiteline gear:
http://www.whiteline.com.au/do_segue4.p ... 3-8%2F2009I wouldn't bother with the W53353, they are just standard replacements