What is it that makes God a secure refuge in old age?
His Honour. He will honour His name in our salvation.
His Command. He commands our salvation and His forces will accomplish it - not our strength.
His Righteousness. His acts on our behalf are alone what secures our salvation. Old age teaches us we need to be rid of any idea of self-righteousness, or that God needs us to contribute to our salvation if we are to be saved. In old age we may not be able to contribute, but that does not matter: His righteousness is all we need.