I've found that this is usually a "staying with a single insurance provider" problem. I usually end up switching every two years or so, but I check everytime my six month renewal comes up. I've found that my premiums pretty consistently go down so long as I keep looking around. The last few times I switched from geico to progressive then back to geico, and the cost went down each time I switched.

Fun fact. At the last call to make sure my insurance was switched over properly, I had the csr angrily explain that in order to get the same affect, all I had to do was ask for a reevaluation of my policy. It turns out that the automated systems that send out your new price every renewal don't do a good job of adjusting the premiums down and you're supposed to ask a person at the company to review things if you don't like the automatic price.

I plan on continuing my personal policy of switching providers every few years anyways. I'd rather have the new customer prices than deal with a person on the phone going through every option to see if the new price is actually better or worse than the competitors offers.