Once planted, a seed will never die. Though conditions may not be able to support the life that it is to bring forth, the seed will survive until those conditions are right.
Like a seed, the promises of God may tarry but they will never die. It may take months, it may take years, it may take decades; but the promise will endure and once the conditions are right, it will spring forth life. It may take faith to receive the promise and it may take a little more faith to wait for the promise, but the promise will come to pass.