Think China's well-to-do shoppers spend precious hours deliberating how to drop that extra $20,000? Think again.

China's upscale shoppers are increasingly impulsive, according to a new report from consulting firm McKinsey & Co, which surveyed 1,000 Chinese luxury consumers in 14 cities during July and August this year. When asked how long they deliberated buying luxury bags, purses or wallets this year, 37% said less than a single day, up from 24% in 2010. For luxury watch buyers, 19% bought on impulse, pondering their purchases in less than a day, compared to 11% two years earlier.

Shoppers pose for a picture in front of a Channel luxury boutique at the IFC Mall in Shanghai June 4, 2012.

Lavish impulse purchases are also more likely to happen on home turf. Chinese travelers, while accounting for nearly half of luxury items bought overseas, plan their shopping sprees, with only 15% spending spontaneously. Nearly 40% of shoppers on the home front are buying spur-of-the-moment indulgences, the study says.

The rise of the impromptu splurge has big consequences for luxury retailers, according to the report. On-the-spot Gucci gorges, Burberry benders and the like are done in shops, which means that the in-store experience is make or break. Skillful sales staff who know how to upsell and ask the luxury version of "would you like fries with that?" are key, says Yuval Atsmon, a principal at McKinsey. China Real Time has more.

Follow Scene Asia on Twitter @WSJscene.