You'll probably go through 3~5 sets of wellgos by the time you wear out a PD-520 or PD-540, if it's even possible to wear them out.
+1 - getting 3000 miles out of a set of pedals is nothing to brag about. You oughta be able to get 3000 miles year for 10 years out of a set of pedals. With the Shimanos it's very likely that you will.