Another point that has to be considered is the elephant in the room.
He is playing online, He is winning and he has not tried to withdraw his winnings. He should be able to withdraw his money at any time. But then again he may not be able. Leaving all of it there will leave it all at risk. There are more players in the game than those that are playing poker. It is better to remove some on a constant basis than allow somebody suddenly say you can't take any. Very few people actually don't mind paying out large amounts, but it is against human nature. While it is on the table or in their account they have total control and total ownership of your money and like a bank treat it as their own.
In business I have handled some quite large amounts and I have always found the same adage. Greater the amount- more you have fight to get it into your own bank.