You WILL want to keep your pool at shock level for your CYA, but if CYA is 30, that would be 15, and if CYA is 100, that would be 25, and with a vinyl pool, if you don't want to fade it, that's important. (My liner is old so I don't give hoot if it fades).
No point in wearing out your SWG trying to clear your pool, but a constant level of chlorine at shock level is necessary.

Carl