First of all, I am surprised there is no "Theory" forum in existence that this would be an appropriate inquiry for.
To answer the question; they just keep going in a never ending cycle...think of it...as I believe you said...."the wiring does not deplete...".
David A Engelhart
Florida Electrical Inspector BN4045 Plans Examiner PX2057
ICC (International Codes Council) Certified 1&2 Family Dwelling Inspector
Florida Fire College and ICC Fire Safety Inspector I and Plans Examiner
2011 President Joseph A Schneeberger/Florida Gulf Coast Division, Florida Chapter, Southern Section International Association of Electrical Inspectors (IAEI).