The way I heard it, HPN was given the task of developing the Paralever system. BMW came to them before it was fully developed and 'requested' what they'd created to that point. HPN told them it wasn't done yet, but BMW had to have it, and so it went. I don't know what problems HPN were still trying to overcome, but it wasn't fully developed in their minds.
On the early paralever castings you could see where a fill and drain plug was to go, so they were evidently considering bathing the shaft in oil just as all the earlier bikes, but decided against it. It's been speculated that BMW was concerned about the rear boot leaking and fouling the brakes.
I've heard of u-joints failing and destroying the swingarm and even the transmission. It can be a dangerous and even catastrophic failure.
The joints could fail much sooner than 40K -I've heard of them going as early as 14K. I fixed one for a friend and his bike only had 18 or 20K.
And yes, it's atrocious forcing the consumer to replace a complete driveshaft for a failed u-joint. At least they seemed to resolve the issue in later paralevers, moving on to final drive failures and other things.
