Al,
I have found, and of course this is just my opinion or my own warped "logic" that the longer a player is "standing" on his prongs the more he loses his tweak, strength or straightness if you will until they "rest" or get "touched up". Also as Mark mentioned, dusk building up can reap havoc on a speed base such as a safety or receiver not to mention the negative effect dust can have on strength...just my opinion but I'm not very bright
Hope that helps...