When you buy term life insurance, you are protected for a particular time. For instance, if you buy a plan with a policy term of 30 years when you are 25 years old, the term life insurance plan will cover you till your turn 55 years old. Post the policy duration, the term insurance plan will cease to exist and its coverage will end. If you survive the policy term, your nominee will not receive any benefits.
In order to let the coverage going, you can either pick a plan that offers a long policy period that covers you for life or opt to increase your life cover at different stages in life.