Yeah, but it only tells you that it wants to restart once.
If you tell it "later" then it won't bug you again until software update runs.
But Windows, well it decided that every 5 minutes it was going to hide my game so I could tell it to get out of my way. If portal were a more active game like an FPS where timing and such is more essential I'd be really pissed instead of just severly annoyed.
Read the dialogue box closer, you can delay it by much longer then 5 minutes.