As for the 3.0 Camry,Solara,Avalon,Sienna sludge issue, it was due to lack of oil changes like has been said. But, the problem came when a customer said "yeah i didn't change it as often as I was suppose to, but my ford,Chevy,dodge, etc didn't sludge and it was maintained the same". Why you ask?
When Toyota was designing the engine they were trying to meet a certain emissions level such as ULEV(ultra low emission vehicle), SULEV, PZEV,etc", in order to meet that level they moved the water jackets further away from the cylinders, which let the engine run a little hotter and it reduced the amount of fuel condensation on the cylinder walls which in turn lowered emissions. FYI-fuel must be in vapor form to burn. if fuel vapor going in to the combustion chamber comes in contact with a cool cylinder wall it will condense back into a liquid, just like a glass of water or a soda can. the liquid doesn't burn and it goes out the tailpipe and raises emission levels. The hotter running engine would break down oil sooner then you average engine would and it would cause sludge buildup.
When I was still at Toyota I had an Avalon customer who drove 40,000 miles without an oil change. The oil had literally crystallized in some areas. when asked why she didn't change her oil she said the sales person told her to change it every 30,000 miles (just a little off) and she didn't see what the big deal was to wait until 40,000. Nevertheless Toyota covered the engine under warranty with absolutely no proof of maintenace. this is why Toyota has been covering these neglected engines well after the warranty period and with very little to no evidence of maintenance. then the problem was compounded when those cars had been leased( an even better reason not to maintain your car)and were being returned to the dealerships which in turn sold them as certified used cars. the new owners are usually THRILLED to find out there certified car was so poorly maintained. so again another reason Toyota stepped up and took care of these specific engines.
Your epic engine is not one of these engines. So maintain it. the maintenace guide says to run synthetic after 200 hours. I only have to change it once a season about 90 hours so why not put the good stuff in it.