Two things:
Been a while since I spent a lot of time in Denver, but I'm pretty sure that this still stands...
DEN to Aspen is at BEST a 3:40 drive. If there are any weather issues in the high country, it could turn to 5-6 hours or worse. When you look at driving it, keep that in mind.
I haven't flown F9 since early 08 prior to the BK filing (although they are my favorite airline...). Still, on most airlines I've flown, the local staff always like to get people out earlier if possible. If you call and try to change a flight, they charge - but usually showing up before an earlier flight the same day and saying "can I get out on...XX" will result in success (if there are seats). Try checking something like SeatCounter to see what the load is. Since the flights don't come up when booking, they might be full...
Also, if your inbound DEN flight is running slow, be sure to tell not only the FA that you have a tight connection, but also step to the counter as soon as you deplane and ask them to call the departure gate - I've done the A56 to A28 run with the plane being held for me...
Good luck and good skiing!
RFTraveler ^