The moment things look like they're coming back, speculators start driving up the price of oil, thus depressing the economy.
This could go on for quite some time.
Eventually conservation and expansion of energy sources might help, of course, but those things take time to get online.
Until we change this fundamental factor driving our economic system I suspect we're reaching the limits of economic growth.
This is very true and makes me wonder if there might not be some external influence driving them.