Easy environment, mostly easy highway cruising, this can easily go 15,000 miles.
Here are the odds (approximate) that you would ever have a warranty issue with Toyota over an engine failure:
---- First, consider they would ever question your oil changes in 1 out of 2 engine failures, 0.5 factor. (Usually they just look at how clean the valve covers are & oil color, dipstick level.)
----Second, your chance of ever having an engine warranty claim that involved a lubricated internal part is 1 in 1,000 vehicles, or a factor of 0.001.
----Your final odds are: 0.5 x 0.001 = 0.0005.
Conclusion: If you extend your oil changes out to 15,000 miles, you have a 1 in 2,000 chance of ever arguing with Toyota over oil change intervals. Its your choice of whether those odds good or not.
[[[ If the "real" odds of a Toy engine failing is really 1 in 500, and not the 1 in 1,000 I've stated, your odds are still 1 in 1,000 of ever having an argument with Toyota. ]]]