Well it wasn't an issue in SAIS, really. The penalty for late return was purposefully high in order to force you to heed it, which then meant that you *had* to make decisions based on how long it would take you to do things, which was a really key aspect of the gameplay.
If you could take as long as you wanted to play each game, you would not have played it in the same way.
I'm itching to get my hands on Weird Worlds... I hope the shipping is quick! It's never fun to have to see everyone else talking about it and still be waiting...