I don't know whether it's been posted before, but in an interview, Van Gaal apparently said:
" Robben has been out for 4 weeks, so half an hour seems reasonable. Even if players themselves often believe they can play a near full match, I don't think they should. "
You never know with Van Gaal though. He also said he'll decide whether to start with him in the last training session before the game.
Every minute without Robben is a minute we can breath a little easier.