That does sound like a ton of fun.
Riding around in the desert for 90 minutes sounds like the best in the bunch, although that is a long time to go racing through personal uncharted territory.
I guess the 30 minute package wouldn't be too bad but it would be over before you know it.
I would like to go on a one or two hour tour and then make a stop-off in the desert by a few shade trees (if there is such a thing out there) and have a lunch break to check out the scenery while sitting still for a bit.
A husband-wife team would probably be fun too...one drives up and the other drives back. That would be a thrill.