My friend has a 2009 2.5L Altima his parents bought for him. It was a used rental car, purchased with around 15k on it. Around 39k miles, he just had his transmission replaced for free under warranty. I don't know any details besides that.
My mother's '07 Altima still has no issues with the CVT. I'm thinking of getting the fluid exchanged by Nissan once it hits around 100k - it has nearly 90k now. It seems the fluid is about
$17.27/qt at Courtesy Parts - a full fluid exchange will quickly become expensive in fluid cost alone. The FSM says there are two transmissions used by the '07 Altima - I'll need to take a look at the vehicle to determine fluid capacity and add 30-50% of that to get a thorough exchange.