That is just ridiculous!
Makes absolutely no sense!
Sweat may affect the handle, but not the bat itself, this sounds more creepy than any conspiracy theory I ever heared, lol
Players change bats time at the time, when they get too used from hitting the table or ground or anything..
But other than that they have no reason (except of trying a new one).
They may have 2-3 bats, but just to prevent the trouble when they get their bat damaged during a match.
Also it is not easy for top players to find a good bat.. For example my friend who represents our country, uses Nittaku Violin and he has 2 bats and now he says its too used and needs new one.. but tryed already 5 other Nittaku Violin blades and still they are not what he needs. EVERY blade is different..
For me they are all the same! (I mean Nittaku Violin - one is just the same like the other to me, not to him)..
They have such a feel for the ball, cant even understand that!