“A perfect nap in the middle of the day,” she declared, “is like a mini-night.”

But while napping may be advisable for most people, a tricky question remains: How long should the interlude be? With naps, as with so much else in life, can you have too much of a good thing?

Another expert at the conference, Eric Nofzinger of Harvard, drew the line: “The more you keep insomnia patients awake during the day, the more consolidated sleep they’ll get at night.”

Fair enough. Severely troubled sleepers should consult a physician about fixing their slumber, perhaps with naps of suitable length folded in. Those with less dire problems can use trial-and-error to determine what napping coordinates work best for them.

As for the lucky rest of you, you’re free — and encouraged — to nap for as long as 90 minutes per day. Beyond that, almost everyone runs the risk of encroaching on nighttime sleep.