We have Frontier 85s for our older two kids. I'm very happy with them. My oldest is 5, 32lbs, and 41in. My second is 2 months from 4 years old, 41lbs, and 40.5 inches. Obviously we don't need that much seat for the oldest, but she has some impulse issues, so I see her being harnessed for her safety for a while, so it will be helpful. My son is a big kid, has worn 5T/5/xs shirts for a while, so we will get our money's worth there too. But it's so easy to use, they can both buckle themselves, and it's a great seat.
Mom to a girl - 6, a boy - 4, and Baby - 2