Many years ago, when I first moved to Denver, I had Progressive auto insurance. I don't remember what they were charging me, but when I called up Amica, I got a quote that was something like half as much as Progressive's, and I switched over. I've had excellent service from Amica for about 8 or 9 years now.
Ed got his driver's license a couple of weeks ago, and when I went to add him to my Amica policy, it would have added $400 to the year, and my total insurance costs (for full coverage with fairly high deductibles) were going to be about $1200. In the meantime, I had pulled up a quote from Progressive that was much less - about $700 for the year for the same coverage.
So I switched to Progressive again.
All this is to say that it might be worth checking your insurance coverage every few years to see if you get a much lower rate with another company (and to ensure that you're getting only/exactly the coverage you want).