We're all guilty of it: that last-minute snag of a product on the check-out line, Amazon, or late-night-TV. In fact, it's such a bad habit that a new survey shows Americans blow an average of $5,400 a year on so-called impulse buys.

A poll of 2,000 American adults commissioned by the online coupon site Slickdeals reveals that we blow more than five grand on as many as three impulse purchases a week. While they're not always expensive -- a last-minute tin of Altoids at the checkout line qualifies, for example -- they quickly add up.

The survey notes that as many as 20% of all purchases made by adults are last minute ones: more than 150 per year, or as many as one buy in five.

What's that cost the average shopper over a lifetime? It's ain't pretty: as much as $324,000, according to researchers.