Assuming by 'episode' you meant a critical illness like cardiac, stroke or cancer event.
Say, in case of a Cardiac incident followed by treatment, the person can get a claim settlement up to the sum insured (if specific sub-limits are not mentioned in the policy), during the policy period. But the following year onwards, i.e. during renewal they will not be allowed to increase the coverage amount. In which case they can continue renewing the same coverage plan for life.
Also in such cases even porting to a new insurer might not be possible, unless the new insurer has a special plan to cover existing cardiac conditions, which will be super expensive too. This is why insurance advisors always ask you to get higher coverage when you purchase the policy at a healthy stage.
But if it's a lifestyle disease, like asthma, bp, cholesterol, diabetes etc. you can still increase your sum insured (coverage) during the renewals.