Since I want to get the big Johnson bandsaw working pretty soon, I took the old blade off and brought it to school, where the instructor had told me I could make another from the school supply.
When he looked at the blade he said that it was still good, and was the type with variable pitch teeth. However, we still cut off two lengths (137" each) to make two additional blades. I had to learn to use the Doall bandsaw blade welder to join the ends. Fortunately there was a scrap blade in the trash bin that I could cut into pieces to practice on. It took a couple of tries to get a good practice weld. The "test" is to bend it and see if the blade snaps at the weld.
I'm not sure how long a bandsaw blade is supposed to last, but given the stuff we cut for modelmaking I'm guessing a long time. So with three blades I should be set.