This is actually incorrect. "Up to date" is defined as full dose (2 shots for pfizer, moderna, etc., or 1 shot for J&J for example) of the vaccine up to 270 days. If 270 days have passed since your full dose was completed, then you need a booster to be considered up to date. The booster does not expire for being considered "up to date", meaning I got my booster a year ago and I am still considered up to date.