Is the Superlift shaft supposed to last forever? Or is the angle going to shorten the life span of any shaft?
Everything wears out in time. The superlift shaft has a double cardon joint in the rear at the tcase end that allows for far better operating angles compared to the stock shaft. The install of the superlift OR RCD or Trailmaster kits drop the differential down so far that that joint is overextended and the angle is beyond the joints operational angle, and causes a bind in that joint.
Double Cardon is basically two u joints to form a really nice high angle joint. If you look closely at alot of dual purpose trail rigs, they all tend to have double cardons.
Here's a pic of my shortened 95-99/00 explorer front shaft versus a stock ranger shaft:
And a shot showing the new shaft and the adaptor...
And YES the superlift shaft fits a stock unlifted truck. Superlift shaft IS a explorer shaft shortend and uses the same adaptor I used.
Heads up: if you plan on getting a manual transfer case, I highly suggest installing one when you're ready for a new front shaft. That way, if you get a 1354 from a 97 and older explorer, all you'd need is the front shaft from that donor truck....no special adaptors needed since the case has the correct front output on it already. You only need an adaptor if you've got the stock 98+ tcase with that stupid 'ball rotator cup' front output. That way, you dont have to spend more money in the long run on yet another front shaft to replace the one you can't use anymore(shorted expo or SL) and the adaptor.