Standard life assurance policies are what they say on the packet - they pay your estate or named beneficiaries a sum of money if you die within the term covered by the policy. If you outlive the term then you get nothing. It is a cheap way of ensuring that in the event of your untimely death, your dependants are covered against the loss of your income. These type of policies have no cash-in value - it's like motor insurance.
Life assurance policies with a savings element are a very different type of policy. In addition to the life insurance element, they are designed to build-up a sum of money that is paid out when the policy matures.
If either type of policy is not claimed on maturity, then the insurance companies put the money aside. You are entitled to claim it even years later, if you can show that the death occured within the term of the policy in the case of a standard life assurance policy or in all cases for a savings life assurance.