So, here's my scenario:

I'm flying out of IAH at ~7AM on Saturday. I want to go Friday instead because some meeting were canceled, but it's not worth the $700+ in fees. Tomorrow morning, I plan on switching to the 730PM flight on Friday for $25, as long as the open seats remain. After I make that switch, can I again pay $25 to take a 4PM flight out of IAH on Friday? Continental's policy reads, "The same-day flight change option will be available within 24 hours before your original scheduled flight. Inside of this timeframe, you can try to take an alternate flight so long as it departs no more than 12 hours from when you are making the request."

So, can you keep making the changes pushing the flight by 12 hours & paying the $25 fee, or its it limited to once per segment?

Why not just do the switch once, any time after 4am on Friday?
[edit] - sorry, any time after 7am Friday, missed the fact that the original departure was 7am. It's a 24 hour change, not 12...

Thanks for the response... I misunderstood the terms. I was thinking I could change it to a flight within 12 hours of my original flight. I don't know why I was thinking that.

Your original question is still an interesting one though - I've never tried changing after I've already used the confirmed standby... Does anyone know?