'Pro Nighters' are often insomniacs, or extremely dedicated, or the important event's start time drastically conflicts with a normal sleep cycle.
Pulling a 'pro-nighter' is usually saved for important events such as job interviews, sales meetings, or court; or any event where the long term consequences of being late are far more painful than the short term discomfort of not sleeping.
An "All-Nighter" and a Pro-Nighter" are similar but differ by the priorities of the START and END times of the sleep affecting activities to be performed.
A Pro-Nighter ignores sleep to START an important early morning activity. Whereas the All-Nighter starts an activity and continues it on through to the END without sleep.
"He has to be a 'pro-nighter'! If he is here at work this early he hasn't gone to bed yet."