Aside from having no sludge, were you able to verify there was no premature wear in the rod bearings? How about the cam lobes?
What about the oil? Were you able to verify the oil additive pack was still sufficient to protect your engine? How about verifying the oil still had a 30 viscosity and didn't sheer down to a 20 weight?
This is the danger of listening to posts on the internet or making blind assumptions that just because you haven't had any "issues" YET... doesn't mean you aren't causing premature engine wear by extending your oil change intervals past Toyota's recommendations. Oil and oil analysis is cheap, engine repairs are not. An oil analysis would be able to tell you if the oil's additive pack is still sufficient, any premature wear is happening (ex. excessive lead in the oil), and if your oil is sheering. I will never understanding blindly assuming you can extend your drain intervals by 7000 miles because you don't hear a knock from the engine yet just to save $18. Once you DO notice a problem it's too late.
This is not an attack on you derekdevasia but others should not follow your oil change regiment just because your engine hasn't blown up yet. That's as reckless as telling someone "It's been 200,000 miles since I changed my timing belt and I haven't had any issues yet. My wife's 02 has been pushing 250,000 miles on her timing belt without issues!"