benduwan said:
how long would vader wait for luke?hours??

I’m taking the Emperor’s commands literally:

EMPEROR: Then you must go to the Sanctuary Moon and wait for them.
VADER: (skeptical) He will come to me?
EMPEROR: I have foreseen it. His compassion for you will be his undoing. He will come to you and then you will bring him before me.

Also Luke’s conversation with Leia:

LUKE: Vader is here…now, on this moon.
LEIA (alarmed): How do you know?
LUKE: I felt his presence. He’s come for me.

So Vader is on the Moon before C3PO tells the story and really waits for hours.
Remember that Vader is being played by the Emperor.