"The can was a mixture of propane and butane. "

Holy shit! I always thought it was some inert gas. and I always made sure I used plenty of Protectan in my closed darkroom to make sure the chemicals didn't oxidize! When I get home I'm going to read the label on the can. and to think I was more concerned about using pyro...

It's been my experience that even working strength RA-4 tetenal lasts 2 months in a bottle without a problem.