It may be time to buy the iRumor and sell the iFact.

With Apple Inc. set to unveil its latest blockbuster device Wednesday, the iPad3, a window isn’t only opening on one of the most-profitable periods to own the red-hot stock, but also a rare one to sell it.

Granted, selling Apple stock short usually has been an invitation to, in the Wall Street vernacular, “have your face ripped off.” Even not owning it has been perilous for long-only fund managers. Holding every stock except Apple in the S&P 500 would have lopped 0.7% off a manager’s performance last month, according to Bank of America, equal to a typical monthly market gain.

The periods around Apple product launches are different, though. Ever since Apple’s iconic iPhone went on sale June 29, 2007, investors and consumers alike have developed a Pavlovian response to product launches.

Apple’s stock surged 6.85% the week following the iPhone hitting the shelves. Since then, investors have tended to buy Apple’s stock as soon as a new gadget is unveiled.

The period between Apple product unveilings and their actual availability, anywhere from nine to 66 days, has seen an average gain in the stock of 4.53%. So Wednesday’s iPad 3 debut may be an especially good time to buy or increase a stake.

The last two upgrades to the iPhone and iPad took only about seven business days to go on sale. Just counting the week before the on-sale date, Apple’s stock gained 2.9% on average.

Lest Apple’s parabolic rise suggest otherwise, the stock’s typical weekly gain is nowhere near 2.9%. Had it kept that pace over the past decade, Apple would be worth some $29 trillion today, or around double all U.S. stocks—well beyond even the most-delusional Wall Street thesis. On a weekly basis, Apple’s actual compound average gain has been 0.74%—still enough to multiply an initial investment 45-fold.

And when does the selling opportunity arise? Aside from the original iPhone, the average one-week performance after all iPhones or iPads actually went on sale was negative-3.5%.

If history is any guide, maintaining Apple’s pace of appreciation will be next to impossible. Anticipating a rare bout of weakness in its share price may not be.