I plan to keep this car for at least two years after I pay it off. And I always pay them off at least a little bit early.

I kept two of my cars for ten years. I can see doing that with my Prius as well, but there are no guarantees.

I typically keep my cars 3 or 4 years. I am planning on getting the Ford Escape when it comes out and lease it for 3 years. Given how fast the technology is changing and where it might be in the near future, I don't want to lock myself into something for too long.

Support the Troops - Drive a Hybrid!

At this point I am leaning towards keeping the Insight until it dies. But I regularly run through a decision (i. e. dither).
Normally there are only my wife and me to transport, so a two seater car is adequate. When the mother in law visits, a back seat is needed. That's when I consider the four door and five door hybrids.
When I carry a pet to the vet, or carry trash to the dump, or chauffeur the mother in law, I grab our 1994 Land Rover Discovery (148,000 miles).
We tend to keep cars a long time. My previous cars have been transferred to my brother. My wife's cars have been traded in.
When my wife and I met, I was driving a 1976 Civic hatchback, she was driving a 1978 Accord hatchback. At over 120,000 miles, the Civic went to my mechanic brother. I got a 1986 Toyota pickup. My wife wanted something utilitarian to match the pickup, and traded for a Suzuki Samuri. When she decided to invite her parents on our vacations, we took both vehicles on vacation.
My wife was unhappy when I told her about Consumer Reports and the Samuri. She traded it for a 1994 Land Rover Defender. A Defender and a pickup gave us no vehicle with a back seat, so four people on vacation would have required a two car caravan whereever we went. I was unhappy to give up the pickup, but we got the Discovery.
As the Discovery got mileage, my wife wanted to replace it with another one, but she humored my desire to get the Insight.