And that "turn it up' idea is not a rule, most people like to leave their flame
level alone, so when it gets weak, they just fill er up. This actually begins
to produce the need for the purge, ironically. But it sure keeps you from
running OUT of gas when you are away from your butane can, and that is
most important to most people.

Once in a while though, a purge is a good
idea.