Inexperienced operator!  My O gauge track is 133 feet of run loop and circles my living room, dining room and kitchen walls above the doors and windows.  I have 16 gauge bus wires that connect to every 4-6 fastrack section with 18 gauge feeder wire.  Transformer is GW-180.  I have/use 2 locomotives, one is single motor, one is dual motors.  I recently replaced all wires and connectors, cleaned every track section, and upgraded to the above wire size and transformer due to the following issue which still has me scratching my head.  Changes did not resolve issue.
  problem: Unless I continue to increase power, each complete circle by either locomotive takes 1-1.5 seconds longer than the previous circuit, until the train eventually stops due to lack of power.  I clean all 3 rails of the track as well as the wheels and center rail contacts on the locomotive with alcohol and all is good, but it just resets the cycle.  Question!  Should I have to clean all the track and locomotives every 1-2 hours of run time?  Seems excessive.  I have not cooked in the kitchen since before I started the upgrades (about 4 weeks) to see if that had an effect, but no change.  Please advise or at least postulate.  Thanks.