He mentions in one of them that he does rehearse them. Which is for the better, I wish all youtubers respected their audience enough to actually deliver in a professional manner.
You beat me to it.
Yes, he admits to rehearsing them. Still pretty impressive, considering some of the rants are over the 20-min mark and coupled with the distraction of driving while delivering them.
If you like Stan's rants from inside the Humvee, he's also now doing shorter versions on foot during his post-meal walks.
He's also a regular guest on Mark Bell's podcast, with additional appearances Mike Dolce's, Steve Austin's, and several other shows.