Depending on what depth wheels you go with
Depending on who's marketing you believe
Depending on how long you are out on course for (aero wheels will save more absolute time for slower riders, because you are out on course longer enjoying the aero benefits longer)

Over 180km, you might save 5-10 minutes over a normal box rim set of wheels? (MIGHT, again, depending on what you believe....)

Up to you whether or not it is worth it. And, the above comments apply regardless of your power output or position on the bike. Your wheelset has no idea what position you are in... :)



Flo gives some time savings estimates at the bottom of this page:

http://www.flocycling.com/aero.php

Edit - updated my time savings estimate, as I forgot that flo's data is for a single wheel, not a pair...