How many teeth whitening sessions do I usually need to see noticeable results?

hello!

Lately, I've been a bit self-conscious about the color of my teeth whenever I look in the mirror, so I'm considering getting professional teeth whitening again.

I searched online and found some places saying it works after just one session, while others say you need at least 3 to 4 sessions for the discoloration to properly fade, so I'm not really sure.

I received the One-Day Whitening treatment three times in a row.

For those of you who have actually received dental whitening frequently, how many sessions did it take to feel truly satisfied? I would also be very grateful if you could share your experiences regarding tooth sensitivity and how long the results last!