Our youngest turned 8 on Sunday, and there's a bit of a procedure that comes with that - the removal of the child car seats. My wife commented on Sunday morning that it was kind of sad, it was one of the last things left of this age of his toddlerhood, and since he's our youngest and we are not planning for any more children, it's the last of this stage for us as well. I guess it is kind of sad, but frankly, I like the flexibility of my car WITHOUT car seats too, since we find ourselves sometimes driving more than just our kids to places, and the car seat took up a bit of space.
My wife is likely to find it sad again in a few months as our oldest turns 12, because Pennsylvania state law allows a 12 year old to sit up front in the passenger seat and there will likely be many, many challenges about her sitting up front (instead of my regular copilot) on family trips in the future.