Many states have statutes that limit the time to file an action against a lawyer. The statutes many times have statements in them when a person would responsibly know an error was made. Or for example, in Michigan, plaintiffs have 6 years after the date the alleged malpractice was committed to bring suit regardless of when it was discovered. So depending on the state the lawyer is practicing and the circumstances the statute of limitations varies widely.
In some states, if the attorney has represented a minor, the statue does not start until the minor is 18. So in those states depending on the areas of practice, for example with estate work which is one of the longest differences between the covered act and the discovery of the error this date can be much longer than 2 years.
The reality is that for most legal malpractice insurance carriers, they have a 5 year premium “step rate". Meaning that after 5 years of continuous claims made professional liability insurance coverage the individual attorney is considered “fully rated”. Once “fully rated” the attorney malpractice insurance premium will not increase because the of prior acts date. Changes in premium from that point on, either up or down will depend on changes to the areas of practice, claims history, the insurance carrier’s overall results, reinsurance rates for legal malpractice, and/or location of the attorney’s practice.