Teeth whitening

I have been interested in teeth whitening since I was young.

It's not like I'm particularly sick or uncomfortable, so I've just been living like this until now. I used whitening toothpaste occasionally, but only at those times. Lately, I dislike how my teeth look yellow when I smile, and it's bothering me. A friend told me that whitening can make teeth feel rough and brittle, is that really true? I'm not in my twenties anymore, so is it just a pointless thing to do?