With the engine never getting up to true operating temps, the very short commute, etc., I'd be worried about fuel dilution, water, and acid build up running on conventional oil for that long. I'd suggest a UOA as well to get you in the ball park of what is 'really' goind on with your oil.

The only problem is, it'd be another year before you could check it if you are only changing yearly.

Even on my old jeeps that I drive very low miles on annually, I change at 6months on conventional high mileage, after seeing a UOA on oil I'd left in one for a year....it was ugly!

 

Shouldn't the owner's manual state the procedure for mileage and time intervals? Most do, and I assume Lexus does too. There is usually a command for the amount of miles driven OR time that has passed since the last oil change. It's to be which ever comes first.
Alas, doesn't the computer calculate driving habits and pop up the warning accordingly?

 

Not sure if the computer takes into account driving habits. I think it's based simply on how many miles have been driven. Not 100% sure though. But the first oil warning came at 5000 miles for me.

 

It's purely miles. There's no intelligence to the Lexus OCI calculator.