Nothing; Only regular maintenance. I replaced the original brakes at 74,000 miles! Replaced the battery at 72,000 miles.
This is the best car I've ever owned, love it! However: Nothing is perfect, they're costly to keep up. Oil changes are more expensive than other vehicles, and so are other things.
The Infiniti dealer service prices are extremely high. You can go to Nissan and generally get better deals. Or better yet, DIY. An oil change using conventional oil (which is what Jiffy Lube and other chains use) with OEM oil filter bought online will run you about 20 dollars and take 15 minutes. Synthetic + oil filter will run you about 35.
No need to pay the dealer for an oil change. Find a local independent mechanic and an oil change will run you about 19-20 dollars. As much as the dealership wants you to think otherwise, there's nothing special or different about the G20's powertrain that would require more expensive services. It's actually the same engine used in some models of the Nissan Sentra!