Thanks so much for the responses, y'all, even if they were just to call us crazy. ;)

We actually saw the Grand Canyon on our first trip -- not our second one -- when we took I-70 to Vegas. We looped down to see the Grand Canyon and came back up into Colorado. That trip was not as quick as our last one. We actually took 6 days each way.

The reason we shortened our trip so much the second time is because hubby felt that our first trip was a little TOO leisurely and that we could do it much quicker the second time. We kind of overestimated ourselves and overdid it, though.

I don't really want to shorten our time in Vegas -- and we did already book our hotel. We're actually going to three UFC fights in a row (Dec 10, 11 and 12) because my husband is a UFC freak. Between going to the fights and going to the weigh-ins and such, 3 1/2 days are going to be pretty much JUST UFC. Even though we've been to Vegas twice, we've never been able to do everything that we wanted to do. I'm thinking that the first day that we get there, we will be tired and won't do much. Then, we'll have 1.5 days to just do the stuff we want to do there, then 3 days of UFC fights, then 2 more days to do "stuff." So, maybe it's not quite as excessive as it seems?

We're not necessarily on a tight time schedule because we're both self-employed and are planning ahead for it, but there does come a certain point where a trip is a little too long and you're just homesick. I'm thinking 4.5 days -- arriving in Vegas on the 5th day -- will probably be okay.

Oh, and now we are actually thinking about taking I-70 one way and I-40 the other. Hubby would like to visit Colorado again. I'll talk to him about maybe heading to the Grand Canyon again.

Thanks again for everyone's input.