As I get older, I become worried about yellowness.

Maybe because I often drink coffee, my tooth color, which wasn't very noticeable before, looks particularly yellow. So I'm also concerned about smiling and can't smile broadly, which affects my confidence a bit. I used to think teeth whitening was only for young people, but I never thought I would have this kind of concern. How many sessions of teeth whitening are usually done? What is the satisfaction level of those who have tried it? Also, I've heard that whitening can be bad for teeth; is it safe?