The flip side of the coin - try THIS on United:

If you think that you may be traveling earlier, buy -2- advance/discounted fare tickets on Southwest, one at the earlier time and one at the later time.

The ticket you do not use turns into a credit worth 100% of what you paid, with no $100 change fee. It can be used for a future flight on that route or any other route. United tells you to just throw unused tickets away, because the cost to change them is often more than they are worth.

Call up United sometime and ask them for a credit of all of the segments you never flew. Hear the agent guffaw loudly before hanging up on you.