(i) After long use, the wires get heated up due to heating effect of current. This increases the resistance of the device resulting in consuming more power.
(ii) Manish is fully justified with his act because the device requires higher potential, thus it efficiently decreases.
(iii) Manish is a highly concerned, sincere, alert and sensible user of electricity. His friends need to look into the cause and reason of such practices instead of making fun of him unnecessarily.