For whitening care, should I do it intensely? For a long time? How much should I do?

I feel like I'm always consistently doing whitening care.

I use sunscreen as a basic step, and I also use whitening products for my skincare routine.

I mainly use whitening essences and serums, but even though I apply them every morning and evening, I don't really notice any effect.

I've been using it because the ad said I'd have porcelain skin in 7 days, but maybe my eyes are dull, I don't really notice any difference.

Should I use these products intensively morning and evening for a short period?

Or I am wondering if I need to use it for a long period, whether it is 3 months or 6 months or more.