Do I only need to undergo teeth whitening treatment once?

I'm interested in teeth whitening. If I only undergo the treatment once, will my teeth become clean, or do I need to receive regular maintenance for it?

Since I really love coffee, my teeth gradually turned yellow over time.

Is it because teeth also age as we get older...

My teeth are yellow, so I feel self-conscious even when I smile.

Is teeth whitening treatment something you should try? Do you only need to do it once?

How much does it usually cost?