Eternal in a sentence as an adjective

No, the price of liberty is eternal vigilance.

I feel fortunate to be an eternal optimist who knows these things are temporary, but the startup lows are about as low as they come.

Actually, not only true but expected:"The price of liberty is eternal vigilance.

Eternal definitions

adjective

continuing forever or indefinitely; "the ageless themes of love and revenge"; "eternal truths"; "life everlasting"; "hell's perpetual fires"; "the unending bliss of heaven"

See also: ageless aeonian eonian everlasting perpetual unending unceasing

adjective

tiresomely long; seemingly without end; "endless debates"; "an endless conversation"; "the wait seemed eternal"; "eternal quarreling"; "an interminable sermon"

See also: endless interminable