USAirways does. But they have FOUR tiers of elite status, so the lowest (Silver) usually are left sitting in coach anyway. But the point is - no US Elite customer has to pay or earn upgrades. They are "unlimited" as long as the seats are not purchased by full fare passengers - and the higher elites don't snap them up. Also, any elite on US can upgrade to F on a full Y/B fare at time of ticketing. Frankly, it's a crappy program and US' F product royally sux compared to any of the other "legacy" airlines in the U.S.
As for lifetime Gold, I'm almost there. But let's all remember that "lifetime" means the life of the AAdvantage PROGRAM. If AA is gobbled up by someone else in the future, all bets are off. OR, if AA totally revamps the program and renames it (which they are legally entitled to do by the T&C), all the lifers are S.O.L.
Those are UNLIMITED UPGRADE REQUESTS a very different thing. And since everyone has them for the asking the competition is fierce. By controlling the flow the way AA does with stickers, you can actually get upgraded as a GOLD quiet often.