How often should I shop my insurance?

The short answer is every year.

Either you or your agent should be reevaluating or shopping your insurance pricing every year.  Regardless of losses or not.  Who wants to over pay for insurance?  The long term opportunity cost of over paying $100-$500 a year could be quite expensive to you for your loyalty.  If anything your loyalty should be a discount on your insurance costs.

Using an Opportunity cost calculator to determine your personal situation can help.  Here's an example, if you spend $100.00 on an over expensive insurance product, and you could otherwise invest that money for 30 years, then spending the $100.00 could cost you $231.35 in forgone interest earnings. This would bring the real price-tag of what you are spending your money on to $331.35. So the question you should ask yourself is: Is what I am spending my money on worth $331.35?

With new tools out there like Compare.com owned by Google, it will be easier to obtain quotes and compare different carriers pricing.  

Now if you have had good experience with your BOP, personal auto, or homeowners policy and have not filed a claim - you hold the power with your incumbent carrier.  Please note, it is more expensive for a insurance company to acquire new business vs. retaining customers therefore they can't afford to lose you.  

If you have filed claims, you should still have one ear out in the market listening for insurance carriers who feel comfortable with taking your risk for a lower price.  It provides leverage in the negotiations as well as keeps your counter-parties fair.   

Now here's the part where having an agent or broker is helpful, always make sure you have the same limits, terms, coverages, etc.  Financial strength of your carrier is also an issue to explore, for long tail lines- you need to make sure your carrier will be around to pay your claim.  

Whenever comparing quotes.  The qualitative comparison is still something that a computer cannot replace, humans have intuition and experience for where a individual or business can have exposure to loss.  It's this experience that is priceless when procuring insurance, no one wants to be in the position of having to pay for or explain an uninsured loss.  Shareholders, spouses, and bank statements will all suffer in the event of an uninsured loss.  

An insurance consultant is a good option, InsuranceShark partners with the consultants at HMG Consulting and thinks they have the right combination real world expertise and solution oriented thinking in insurance and tax related matters