You're close. It's 24 months after commissioning for LTJG, and 48 months (total) for LT. The 3 year raise I was referring to was the oddity in the military payscale. The pay scale in general increases your pay every 2 years, but if you look, there's a raise for 3 years. That's what I call the navy's retention weapon. For people with obligations that end after 4 years, giving them a 400-500 dollar raise at the 3-year LTJG mark gives them something to consider.
As for eating lobster tail and steak, they have that in the wardroom too, but that's not an everyday meal. Some meals are better than others.