As long as you were honest when you filled up the application for your life insurance policy, the life insurance company is obligated to fulfill the terms of the policy contract.
If you were a non-smoker when you applied for the life insurance policy, then there shouldn't be any problem.
When it is time for your beneficiary to file a claim, they will pay the entire death benefit. This will be, of course, after the life insurance company has investigated the cause of your death.
Smoking the occasional cigar will not really show up in your death certificate. So there is no reason to fear that your life insurance company will not pay a claim if you die.