I'd love to say it's not sage advice, but it is. Unfortunately, once people know your age they will – consciously or subconsciously – treat you differently. I rather quickly opted to never disclosing my age in any context, unless it is absolutely necessary (it almost never is.) It's just easier that way, leads to less discrimination. Unlike skin color or other highly visual traits, it's one aspect of your person you can hide without any significantly negative consequence.