Your insurance policy should cover a person till the age he intends to retire. Till a few years ago, this was 60 years. However, in our new age we may have late marriages and having children at a higher age mean responsibilities do not end at 60. Experts suggest a life cover till 65 years, though it may vary according to circumstances.
We will not recommend you a short-term cover of 15-20 years that ends when you are in your 40s. The premium will be very low because you will be insuring yourself for the non-risky years. 40s are perhaps the time when you should have the best possible coverage. If you take fresh insurance at that age, it will be very expensive. You might even be denied a policy because of your health.