My sister has a 2006 Mazda 3 she bought new. It has been in VT all its life and has been driven in winter every year (she puts snow tires on it).
This year will be its last on the road, at least for my sister. It needs $3000+ in rust repair to pass its next state inspection. The exhaust system is shot, and has already been replaced once. I believe it has had other rust repairs as well, and I know it has other rust damage.
To the car's credit, it never got undercoated in its life. My sister just wasn't aware of the extent of damage rust causes, and certainly wasn't aware that Mazdas are more rust prone than other brands. She isn't from the Northeast and the car was her first big purchase after moving there.
My parents are selling her their 2008 Mazda 3, which has been in NC all its life and is totally rust free. It will be undercoated as soon as it gets to VT. My sister loves how the 3 drives, and aside from rust it has been reliable, but the rusting is a big issue. She had hoped to keep the '06 for 10 years, but the car is totally done at 8.