idler rumble, heat, and record wear--a connection?

At 33 rpm, assuming no significant slippage of the idler wheel against the platter, and assuming there is some sort of mat between the platter and the LP that ought not to be a very efficient conductor of heat, unless it's made of copper, I cannot imagine that it could be "normal" for the LP to heat up as much as 30 degrees F during one 20-minute play. Something is amiss. I am thinking about the bearing assembly in particular.

Maybe there's a heat lamp hanging over the turntable.

Cocoa, Have you felt around among the various culprits we've mentioned? The thing that is hottest may likely be the source of the heat. If the LP is very warm due to the motor, the motor must be very very hot, for example. If you own or can borrow a high quality multimeter, many of them have an optional heat sensor which permits very fine estimation of the temperature of any object. But meantime, just feel around under the tt (with the plug removed from the wall socket) after a few hours of use. Check the platter, the bearing assembly, the motor. One or more of those is going to be very "warm".