My indy is an ex-Porsche shop foreman and has his own shop now. He does the replacement and is neutral on advising for/against it. He has done quite a few now and he has pulled out a few that were failing.... no noise or symptoms, but clearly failing. These engines were clearly saved. He also pulled out many more that appeared perfect. So should you do it? I dunno.
Given my value system of keeping cars a long long time, I think I will probably do it when my clutch goes.... if it goes. I have 194K miles on my original clutch..... who knows when that will go as I always rev-match. Even the Porsche mechanic tells me it is like buying life insurance. Do you really need it? Only you can answer that. He has said, going way back, that he has never seen engine failures to the high degree from these engines.... I don't want to open the debate as to "how frequent" etc. but he said that when you compare the engine failure frequency of these engines with past Porsche engines, there is no comparison and he was shocked at what he feels is just cheaped-down engines. He said the fundamental reason for these failures is that Porsche just cheapened them.
When I was in Altanta, having my failed engine replaced at 47K miles (2000 S), there was a poster at Don Ellis Porsche there in the service lounge that read something like "All Porsche parts are race tested". No more.
Oh, they were working on one of the engines they saved and showed me the bearing... awful looking. He said, and showed me the intermediate shaft... they saved the shaft by doing some machining to the end where the bearing was failing and was grinding it up. Fortunately, the pieces had not entered the engine. They told me the price of the shaft... don't remember but it was expensive. Apparently this one made noise.
Even seeing this carnage and hearing the stories first hand, I still won't do it unless I have the clutch replaced. Again, the mechanic was neutral about it as there are still a heck of a lot of engines still humming away nicely.