Hey, Jay - me too. In very slow rush hour traffic I stay in a super-low gear so the rev's stay over 5000 rpms.
ImOK:
I have read that a dead battery can't be fully recharged by running the engine at high rpms; instead they say that only a trickle charger will fully restore the battery.
Also, a battery can't be reliably diagnosed for having low voltage merely by confirming the operation of the lights. However, if the headlights were used for the test and run for 5 or 10 minutes then that might confirm it - but now your killing the battery even more - so don't use that test either.
I bought a super-small voltmeter (multimeter) which I carry with some basic tools in my tail bag. That is the only reliable test. I believe a healthy battery should be at least 12.5 volts. If the voltage is below 12.0 volts than this constitutes an exhausted battery, and the starter motor is too weak to turn over the motor. Time to bump start her.
Reference:
http://www.sampson-sporttouring.com/voltmeter.html
Summary:
Battery type = Lead acid
Over-discharge, danger = 10.5 V
At dormancy = 12.5 V
Charging, min = 13.5 V
Charging, max = 14.5 V
Over-charging, danger = 14.8 V