[VAL] can propane go bad?

[joepatwink@xxxxxxxxxxxx (Joe Winkler)]

Of course I don't mean bad as in writing checks on their mother's 
checking account or kissing and telling all. I mean can propane 
lose it's burnability over time? We took the camper out for the 
second time this weekend. It still has the same propane from 18 
years ago, which is when it was used last. The hot water heater 
lost its flame two times, the oven pilot and stove pilots went out 
five or six times, and the furnace flame quit three times. Both the 
hot water heater and the furnace flames died while running, the 
pilot light goes out and then the gas gets shut off because the 
pilot light isn't heating the sensor. Before I purchase various 
sensors and orifices for the different appliances I thought I would 
check with the group. Anyone ever been in this boat before?
  Joe