Here's some good info about pending offers from the Cash Crate Forums:
Q: What does it mean when an offer is Pending?
We provide the “Pending” feature only as a way for you to track the offers that you’ve done. Just because an offer is Pending does not mean it will be credited, and even if you forget to submit an offer to us, you’ll still receive credit for the offer when the company reports to us.
You may have noticed that it’s possible to submit offers to us (and give them Pending status) even if you haven’t completed them. Remember that you will only be credited for the offer when the advertiser notifies us that you have completed the offer.
Q: How long do offers stay Pending?
An offer stays pending until we receive credit for it or until two weeks have passed. If two weeks have passed without crediting, it will be removed from your Pending list and put back into your Available Offers list so you can complete it. If that same offer is eventually credited to us, we’ll credit your account regardless of whether it’s Pending or not.