I was interested in running dedicated snow tires. A few months ago, there was a member who upgraded his wheels, and he was selling his OEM wheels really cheap. My plan was to buy four extra wheels to mount the snow tires permanently.
After I figured out what a pain in the butt and added expense the tire pressuer monitor system (TPMS) would be, I bagged the idea. I believe each TPMS transmitter (located at the base of the valve stem, I believe) cost about $120 or more. Then, the dealer charges something like an extra $100 or so per tire to "program" it. After all was said and done, the stupid TPMS set-up would've cost me close to $1,000, and that didn't include the wheels or the tires!
If you don't have the TPMS transmitters in place, then the TPMS warning light will remain on constantly, or at least that's my understanding.
I wish Toyota would have taken into consideration the fact that some people would like to have the ability to have an extra set of snow tires/wheels without needing to spend a fortune for the stupid TPMS. I guess you could switch back and forth twice each year with one set of wheels, but that gets expensive too.
If you do decide to run snow tires, I have had great service from Nokian snow tires on vehicles other than the 4Runner.