Recently got a six foot USB cable from Amazon for under $5. The stock cord is three feet and a bit restrictive for using iPad while charging. Noticed it takes about an hour longer for full charge. Not a bad trade for the convenience.
Then got to thinking. The charger doesn't get as warm while charging, and therefore suspect the battery also doesn't get as warm. Since the house can be as much as ten degrees warmer during the hot summer, might not be a bad idea to go easier on the charger and battery. So that's what I is doing in the hot times; using the longer cable.
Just sharing some thoughts and observations.