Lyric discussion by WantedMan 

I think this song is fairly easy to interpret. It is about purpose. Fire is usually associated with desire and passion. The old people in this song are realizing their end may be near and they want to have lived for something because material possesions don't mean anything in the end. Thus they are not looking for the "mother lode" as the naive singer assumes, but fire.

I think you're spot on.

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