I believe that, in terms of NRA membership, the actual term is a "life" member rather than a "lifetime" member. I have no idea which term he used.
AFAICT, it's a membership category that gets you membership for the rest of your life regardless of when you buy it.
Romney joined the NRA in August 2006, then began boasting that he was a “life member” of the NRA.
As with much of his rhetoric, intended to lead the uninformed listener to believe something that’s not true.
“I was always for life.”
“I wasn’t pro-choice.”
“I don’t take the position of a pro-life candidate.”
Sorry, I’m getting confused.