Any knowledge of structural/mechanical engineering lends to common knowledge of higher stress concentration around any kind of cut-out of void in a structure. Any other engineer on this forum can back up my statement, as Davidalone has just done. The engineers designing these saddles know about the higher stresses and therefore reinforce the saddle shells to compensate for the higher stresses thus resulting in a heavier saddle, due to the extra material.
I wasn't questioning the issue of stresses around the cutout- I agree with you there. What I am questioning is the veracity of the "wearing out" issue. I think that Davidalone (assuming that I understood his post correctly) was making an unfounded assumption that all the engineers who designed the saddle did was put a hole in it. It is equally likely (or maybe more likely, as you suggest in your post regarding the weight) that the design and construction of the cut out saddle takes these factors into consideration. I don't know of anyone who has complained that their cut out saddle has failed prematurely, or sooner than any other saddle - and in any case, the pleural of anecdote is not data.
As far as weight goes, I think that many of us will agree that a saddle is the one component on the bike where we are most likely to tolerate a bit of extra weight in exchange for greater comfort- or the maintenance of neural function in a "vital organ"!