Declaring the unhealthiness of late nights while staying up late oneself may be perceived as hypocritical, but it also depends on context and intent. Defining hypocrisy requires assessing the consistency between one's advices and personal behavior.
It can be seen as hypocritical to advise against staying up late due to its unhealthy effects while personally staying up until 3 am every night. Hypocrisy involves stating a belief or value that one does not hold or abide by oneself. Therefore, if a person acknowledges the unhealthy aspects of staying up late but does not modify their own behavior, it can be viewed as not practicing what they preach.
However, the situation depends on the context. If this person is trying to change their habits or highlights their own struggle with sleep as a cautionary tale, then it might not be hypocritical. The intent behind the statement and actions of the individual would be crucial in determining the level of hypocrisy.
So, the accusation of hypocrisy involves examining the consistency between someone's statements and their actions. When advising on health, it is generally expected that professionals adhere to the same guidelines they recommend.