I disagree with those who say it is a waste of time to check the oil.
It is not.
Just because you don't find the oil low, doesn't mean you wasted your time. Instead, you confirmed that the oil level is still safe.
I've been following along/participating in some of the Toyota Oil sludge discussions, and while I believe they do have engines that sludge, some of the owners made the situation worse by not popping the hood and checking their oil level.
Heck, my 1994 Geo Prizm (Toyota Corolla Clone with 1.6L 4A-FE engine) has a 3L or 3.2 quart capacity. You go a quart low on that engine and you have lost about 30% of your crankcase capacity. I got into that because there was a guy at Corolland (I'd post the link to the thread but that is a no-no here.) who arrived at his 33K service with 1/2 quart of oil in the crankcase. Sludge problem or no sludge problem, you have to put some blame on an owner who doesn't check the oil in a 3K mile period of operation.
That is SERIOUS.
You check the oil every fill up, not because you EXPECT to find it low, but rather confirm that the engine has the proper amount of oil in the crankcase.
It also helps with early detection of problems.
Finally, I believe it is Bob Salem (you can do a Google search or something, as I'm not sure I can post a link to his FAQ) that said the majority of cars that come in for an oil change at 3K miles are a quart low on oil. Furthermore, if they extend the OCI longer, the oil deficit is much larger as the used oil is consumed faster than new motor oil.
That is my $0.02 on the matter.
TB