I don't believe anyone else on here has posted a way to keep the TPMS light "OFF" other than simply putting a piece of tape over it.
I did some searching on a RAV4 forum, and found a solution. All it requires is a 3.3 kOhm resistor. 1/4 watt or 1/2 watt will work fine.
The TPMS "computer" is located in the dash, directly below the HVAC controls. To access it, simply remove the trim from around the HVAC and radio (pull out at the bottom, as it hinges upwards at the top, then remove the trim around the shifter. Be sure to remove the complete grey plastic piece that also surrounds the A/C 115V switch - not just the silver trim for the shifter. If it's an automatic, you'll need to take it out of park and unscrew the shift knob. There will also be a plug for the light for the shift indicator. On a manual car, you can leave the shifter intact, and just rotate the trim to get it temporarily out of the way.
Now that things are opened up, the module is under the right hand side of the HVAC controls. A 1/4" drive ratchet and 10mm socket will remove the screw attaching it, and you can pull it out. Unplug the connector, and remove the module. On the connector, at one end there is a dark blue wire - this supplies 12V from the ignition. Plug one end of the resistor into this terminal, and then look for a pink wire on the other side of the connector. Connect the other side of the resistor to this terminal. Use some electrical tape to cover the resistor and ensure it stays attached to the connector. I then tied off the connector to the bottom of the HVAC controls to keep it from rattling on something below. Now you can put the computer back if you want, or keep it out, as it's no longer going to be used.
Now just reassemble the dash in the opposite order you took it apart. Turn on the ignition, and enjoy the lack of the tire warning light flashing at you!
This is of course a semi-permanent solution. To go back, you'd just have to go back in there, remove the resistor and plug the module back in.
For next year, I'll probably devise a switch for this, as my "summer" wheels still have operational sensors. It would need to be a 2 position switch. You would need to tap into the 12V wire, and add another feed off of it to go to one side of the switch. The resistor would be installed in series between this wire and one side of the switch.
You would then need to cut the pink wire, and attach the side going into the harness (goes to the instrument cluster) to the center terminal on the switch, and the pink wire going to the computer would attach to the opposite side of the switch from where the 12V and resistor line is connected.
With this setup, the TPMS computer would remain connected. With the switch in one position, operation of the light would remain "normal", still being connected to the computer. In the other, it will have a reduced voltage supplied to the cluster, instructing it to keep the light "off".
That's how the cluster works the light - it's looking for a low voltage signal (approx 5-7V) to be applied through the pink wire to turn "off" the light. If the circuit is open, the light will remain on. The resistor drops the 12V supplied by the ignition to a proper level for this to work without damage. I didn't calculate it - somebody on one of the Toyota forums did - I just took advantage of it!
I installed the resistor on both mine and my brother's cars today. His has some internal fault code set in the TPMS computer ( I don't know the details), but we'll probably leave it like this rather than spend money trying to fix the system. He knows how to use a tire gauge...
My winter rims don't have sensors, so I'll keep the resistor in for the winter, and take it back out next spring. I will eventually install a switch somewhere - the only issue is that the wiring is pretty tight to work on in there without further disassembly - so for the couple of minutes it takes me to pop the trim off, I may just do that again - it's pretty easy.
Hopefully this helps someone else that's tired of seeing the light all season - or just wants to forget the system overall if they have issues with it. Myself I always do a walk around before driving, and check the pressures regularly. If it was a more sophisticated system that actually told me pressures and locations I'd be more keen on keeping it active - but the simple light I really don't care about. One day I'm sure the batteries will die in the sensors anyway, and the resistor can just stay where it is now.