If you want absolutely perfect shimming, re-shimming should be done.
However, having a motor heat up and even smell is somewhat normal, especially of standard 16-TPA motors. You're most likely smelling the brush material or the arcing from the brush-commutator contact.
If these symptoms weren't present before, it could mean that the setup is under additional stress, you have a connection issue (causing a higher amperage draw or a short), and/or the motor is wearing/burning out.