Damn, having both a Tacoma and a 4Runner, this is good to know!
"Therefore with a 23 gallon fuel tank I calculate one can idle for 54.8 hours. To call it safe round down and assume that you can idle for one day with a half tank of gas and two days with a full tank."

Farther down in the link there's a quote from an actual car manufacturing engineer for Ford who states, "We’ve had test engines idling for thousands of hours without significant changes. I’m not sure I have seen anything to back up the idea that excessive idling causes buildup in cylinders or fouls plugs." which is good to hear. I was always told that prolonged idling is bad for the engine. If it doesn't hurt a Ford, it definitely won't hurt a Toyota.
-Blast