DS is 22 months and still RF in a Complete Air 65.
All my friends' kids were turned to FF as soon as they turned 1. At daycare, I don't peek into everyone's cars, obviously, but out of all the other kids in the class that I do happen to see being dropped off/picked up, our son is the only one still RF.
I saw in the thread that a lot of people here have their 3 year olds and older still RF. I think that's great! We'll have to see for how long we can manage it. I already went out around 18 months to replace my car seat because he had outgrown it height-wise. I have an incredibly tall toddler (measured 36.5" at 18 months!); the Complete Air 65 is supposed to accommodate RF until 40", but based on his height curve so far, I'm not sure that will keep him there for another year and half! Then again, I've seen on other forums people saying that the shell of that car seat will allow for taller than that, even though that's what Safety 1st lists as the limit.
I can't say I haven't thought about changing him at this point sometimes. He's having some light sensitivity issues from the sun that shines through the back window, and I'm not comfortable driving with a shade on it. It's probably silly - I'm not sure why I think FF will help with this: there is a big windshield letting sun in from the front, lol! Maybe I'm thinking the seat in front will help provide more shade? (We don't have the seat in the middle because it doesn't have LATCH there). Also, on our VW Golf, having the seat RF means that we've had to push the passenger seat too close to the air bag for any adult to ride in that seat safely. Which means every time we go out as a family, either my husband or I have to sit in the back. It would be nice to ride up front one of these days again...