The problem with life membership (for me, both NRA and ARRL) is that it's a one-time payment, and after X years, that organization loses money on that lifer. No company/corporation/business can continue to exist once its expenses exceed revenue. 

Can you imagine if I'd purchased an ARRL life-membership back in the 1970s -- I think it was maybe $75. The League would have been losing money on me after just a decade.

Jeff KH6O