You can do lifetime for $300 now, and I think the Endowment upgrade deal might be $250.
I'm already a life member, so I generally shrug and toss the mailed offers. My dad has been a paid member for decades, but figures life membership for another 10-15 years of his life isn't worth it.
I'll likely upgrade when I'm older and don't have kids and a wife to keep shod and fed.