I regularly see quite a lot of corollas with 1zz-fe engine - with more than 200,000 miles on the odo (above 320,000 kms) and their throttle bodies never required being touched at all - so much so that their intake manifold gaskets would shrink and cause air leaks due to age, but their throttles are perfectly good - work smooth and perfect.
All cars using regular cheapo 5w30 API SN and cheapo oil filter changed every 3000~5000 miles.
Most manufacturers actually prohibit cleanign the throttle, some coat the blade with teflon (ford, mitsubishi etc) some have teflon bearings in the throttle axle. Dunking it in petrol or forcing petrol into it will cause problems.