But stimulus is supposed to be temporary. It's supposed to "jump-start the economy." Expansion becomes self-sustaining.
In Japan, this transition never really occurred. The longest period of growth (2002-07) depended heavily on a cheap yen that revived the export model.
Richard Katz, editor of The Oriental Economist, calculates that about 60 percent of growth of GDP in these years reflected exports and investment tied to exports. This ended with the 2008-09 financial crisis.
The lesson is that huge budget deficits and ultra-low interest rates - the basics of stimulus - have limits and can be self-defeating.
To use a well-worn metaphor: Stimulus becomes a narcotic. People feel better for a while, but the effect wears off. The economy then needs a new fix.
Too many fixes spawn new problems (excessive debt, asset "bubbles," inflation). That's already happened in Japan.
It's caught in a trap.
On the one hand, it needs stimulus to grow. On the other, the debt from past stimulus measures threatens future growth.
About 95 percent of government debt is held by Japanese investors - banks, insurance companies and pensions - that have been patient, report economists Takeo Hoshi and Takatoshi Ito.
If investors lose patience and balk at buying government debt, the economy could implode.
But their patience presumes that annual deficits will someday shrink. The trouble is that the required tax increases or spending cuts could act as a drag on the economy.
Already, the Diet has voted to raise the consumption tax in 2014 and 2015 from 5 percent to 10 percent.
Given the contradictions, Japan isn't an attractive place for private investment.
A declining population reinforces the effect. Katz of the Oriental Economist suggests spurring growth by dismantling protections for sheltered domestic industries.
Higher growth would emerge as "inefficient firms die [and are] replaced by better firms."
But Japan's leaders have generally shunned this complex and contentious approach. Once the present stimulus fades, Katz writes, it's likely "Japan will fall back to stagnation."
The United States isn't Japan.
The American economy is more flexible and entrepreneurial. The natural gas and oil boom is a godsend. Housing is reviving.
Still, similarities with Japan loom. Growth rates have been stubbornly low. Both countries rely on stimulus policies - cheap credit, big deficits - to cure problems that are fundamentally structural and psychological.
The parallels are worrying.