The fire extinguishers are to buy me time to get anyone in my rig, and myself out.
However, this brings up a good point when choosing a rig. Most class "A"s have one door, with the exception of some like the Winnebago Via which might have a driver's door as an addition. A class "C" almost certainly will have the two cab doors usable, so at the minimum, that is three exits.
It is very wise to practice with the emergency windows. One caution, though: Some rigs have the upper hinges for the emergency windows attached with only some tape, so when unlatched, there is a good chance of the window coming completely off. There is also a good chance that the rubber seal adheres too well, making it very difficult to get out (might try talcum powder.)
