Our standard recommendation / specification is 4 foot post spacing, but you can go up to 7 feet if using a Cable Stabilizer in the middle to maintain cable spacing. The farther apart your posts are spaced, the more cable deflection will occur and this can cause unsafe conditions. Never attempt to use a cable stabilizer on rail sections over 7 feet. Never use multiple stabilizers to attempt accommodation of rail sections over 7 ft.
Cable Stabilizers are not structural and cannot be considered a post, they are to be used for maintaining cable spacing only.