Even Kors eventually will need to slow. The company has generated comparable-store sales growth of about 40 percent for the past three years and expects them to rise 25 percent in the year through March. While companies like Lululemon Athletica have shown robust comparable-sales growth in the past, it has proven difficult to maintain for more than a couple of years.
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Indeed, it's hard to imagine Kors selling much more merchandise at any given store. The company's U.S. stores will probably sell about $2,000 in merchandise per square foot in the year ending this March, estimates Paul Lejuez of Wells Fargo. Coach, by comparison, reached a peak of $1,300 per square foot in 2007, he said.
Kors trades at a heady 27-times consensus forward earnings, though that multiple could drop slightly as analysts revise forecasts higher after Tuesday's results.
Given the lack of other seemingly bulletproof growth stories in retail, investors may be comfortable holding on to the stock at that level. But with Kors stores already selling so much merchandise per store, sales growth may slow sooner rather than later.
—By CNBC's John Jannarone. Follow him on Twitter @jannarone.