T/H mode keeps your trans in a lower gear longer, yes... But that's because it's not UNLOCKING the torque converter which will generate a TON of heat in the fluid in a matter of MINUTES... ;)
So, if you like the fact that you are running in a higher gear, but in an UNLOCKED TC condition, you obviously don't pay attention to your trans temps... ;)
I'd rather run higher rpms in a LOCKED TC condition than a lower rpm UNLOCKED and generating a TON of heat in my trans.... :)
That's just me, so do as you feel works best for you.. ;)
Mitch