God is eternal.
"The eternal God is thy refuge, and underneath are the everlasting arms: and he shall thrust out the enemy from before thee; and shall say, Destroy them."
Eternal means forever and cannot have conditions. Temporal means "lasting until ended" or "lasting unless ended." Can we or dare we put a condition on the eternal existence of God and make God temporal?
Why then do we dare to make His salvation temporal? God says the salvation He gives is eternal just like He is eternal. Forever as God exist, so does the security of our salvation. Salvation cannot be lost.
"My sheep hear my voice, and I know them, and they follow me: And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand."
The never of God is forever.