From God’s perspective, praying an hour a day has no value in and of itself!… There is absolutely no virtue in long praying! Jesus normally kept His prayers short. Only twice in the New Testament did He pray all night. Since both are recorded in all four Gospels, you might think it was eight. Really it was just two different occasions… The shorter the prayer, the greater the faith!… ‘HELP!!!’ is a great prayer!
Andrew Wommack
A Better Way to Pray, Harrison House, 2007, 14.
GraceQuotes.com 
I fully agree about short prayers. And short commands when we’re exercising our God-given power and not actually praying.
But, and this is a very big but, there is a principle of repetition that we must use when understanding the bible.
Very few incidents appear in all four gospels. A few more appear in three. more still in just two. The more a story is repeated, the more important it is.
So the two stories of Jesus praying all night must therefore be very important. I can agree with Andrew about what they’re not teaching. But just to dismiss them like this is very dangerous.