Pearlownz:
Repeated playing often detunes a head, though not necessarily because the head itself is stretching. More likely your tension rods are loosening. Each time you hit the drum, especially if you play rimshots, the rim presses down which takes pressure off of the tension rods allowing them to unscrew themselves, sometimes until they are completely loose. I've tried lug locks (little plastic tabs that fit on the heads of the tension rods and butt up against the rim to prevent detuning) and they work alright, but my snare still detuned.
The best thing I've found are locking tension rods made by a company called tight screw, they have a strip of nylon running perpendicular to the threads that locks inside the lug to prevent detuning. I use them on a
Pork Pie piglite on which I play hard rimshots and they hold the tuning amazingly well. Only caveat is that the tension rod will feel tight as soon as you start screwing it into the lug so you have to rely on your ear and/or tuning gauge (rather than the feel of the tension when you turn you drum key).
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