The more obvious rendering of this verse is, Of old I was instructed out of Thy testimonies, for — not for a brief time, but for ever — Thou didst found them, where for ever expresses indefinite past as well as indefinite future.
Related Commentaries of Psalms 119:152
Psalms 119:152
152 Concerning thy testimonies, I have known of old that thou hast founded them for ever.