My wife recenty became a lifer for $300. If you call it in, ask about time payments, etc. When my wife told them her husband had an L.F., she was offered the $300. deal. They seem to have a variety of payment plans. Do it.
I'm not sure what I paid, but I became a Life Member thirty-six years ago. I was contacted by the NRA in February 2012. They convinced me to spend more to get my Endowment Member status. I'm proud that I have been a Member for such a long time.