Hot Face
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Long drive contestants always have a bag full of drivers - names like Alpha, SMT, Bang and Ashton - built to withstand competitive abuse of swing speeds north of 140 mph. They constantly test their drivers to try to figure out which one will perform best. One of the tests they use is to lay the edge of a credit card across the face of their driver. In time, the driver face begins to flatten. At that point, the face has weakened. That's also the point when it flexes the most, when the face is the 'hottest'. Once the heads reached this stage, they are reserved for competition.
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The flex and hot face mentioned above also known as the trampoline effect... Where USGA has limited it to 0.83 COR..So I guess keep using the same driver.... If change to a new driver, buy it used and always carry a credit card for measurement.... After all, it is true that the more and hard you drive, the further the ball goes...

*source: GolfTodayMagazine.com

USGA Limit on Driver Head Size

As manufacturers discovered how to make driver heads out of titanium balloons, the USGA decided that they had to set a size limit. They chose 460 cubic centimeters. Why?
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A few lesser component companies had released drivers in the 500cc range that looked like something a circus clown would carry. There was no evidence that super-large drivers delivered any performance advantage. Why bother?
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One of the most renowned designers and manufacturers of golf equipment is Katsuhiro Miura. Mr. Miura is the founder and inspiration behind Miura golf, widely regarded as producing the best forged irons in the world. Mr. Miura has planned to introduce his own drivers and fairway woods for several years. In that time, he has studied performance and workability. When his new driver is released in a few weeks, it will be less than 400 cc. Just as skirts always get longer after they get shorter, I predict that better players will be rediscovering drivers in the 400 cc size range in the near future.

*source: GolfTodayMagazine.com