What should be the term in my policy?

If you are 30 right now, buying a policy for 50 years would be an insensible decision. You should buy the policy until your retirement. It is because by the time you retire, very less number of people would be dependent on you financially. While you are young, you have more financial responsibilities, and this is why it makes sense to go for a big cover. But with age, your assets will grow, and you will probably no longer have to provide for your family.