It depends on the state and the type of coverage. There is "occurrence" and "claims made". An occurrence policy is more expensive, but when you stop paying for insurance and end practice or switch to another company, you are still covered forever for all events that took place while you were covered by that company.
With a "claims made" policy, it is initially less expensive, but the day you stop paying is the day the insurance ends. So any event that took place earlier is no longer covered unless you purchase a "tail" coverage, which can then add up. Many companies will automatically give you a tail if you've been with them for over 5 years, but it depends. Most claims made start off cheap and then gradually escalate, whereas occurrence policies generally start off more expensive and stay the same.
I have always had occurrene policies, though they are getting harder to obtain.
I practice in the Philadelphia area, which presently has the highest premiums in the U.S.A. At one point, surgical malpractice in Philly was about $24,000, if a doctor had 2 or 3 past cases against him/her, it could go as high as $40,000 or up, though it has dropped slightly.
There are many variables, so you must check your state.