Consider the sentence [emphasis mine]:
Foreign producers cannot sell all commodities at lower prices than domestic producers for any length of time because the depreciation (or pressures for depreciation) of the importing country’s currency ensures that trade will flow in both directions.
Intuitively, the sentence should mean that foreign producers can never sell commodities at lower prices than domestic producers, because even one day is "a length of time," and the sentence asserts that it cannot happen for any length of time. Of course, that's not what it's actually saying. A more literal phrasing would be "for a very long time" or "for any great length of time."
This interpretation of "any quantity of X" does not carry over to other values of X. For instance,
I would not sell that to you for any amount of money.
means exactly what it looks like it means: that any quantity of money, either very low or very high, is not appropriate.
So my question is, where does this strange use of "any length of time" come from, and are there any other things besides time to which it applies?