Two pages of comments without the "I've been with X since 1970, and they are great" LOL. My in-laws were of that mindset. The wife fell for it, for a while, but I soon learned the lesson that most here have commented on. We got married young, stuck with the family's agent, and one day it occurred to me. As we were developing a history of safe driving, no claims, and aging out of the higher risk brackets, our rates were increasing substantially. I shopped around and found that we were paying nearly double market price for our coverage. Since then, it's become quite clear that the word "sucker" is totally interchangeable with the phrase, "long term, loyal customer" in the minds of many insurers.
Progessive was the cheapest for us while the kids were teens. They then started the typical steep rate climb, after a few years. We switched to another company, and it dropped by nearly half. Last year the last kid left the nest and our insurance is now dirt cheap, but I'll still have to shop once the inevitable increases start.