I think that it really depends on the type of driving you do and also the age of the car.

I always use the weight that the OE lists as the recomended -- this is very important!!. They give this for a reason.

I also have a few cars that do not get much use -- I always change it once per year regardless of the miles.

Our sales cars and our transport cars all get a lot of highway miles, some up to 60K per year, most in the 30K range -- I change them around 5k never before - I use regular oil and have never had an engine go. I do not keep them past 200K.

I have noticed with newer cars the oil is CLEAN, this being on cars with 5QT sumps! I looked at the last 5K change on one of the Nissan Pathfinders with 35K -- you would not believe how clean it was!! I have been thinking that I may start to move towards 7K changes

MB's hold lots of oil -- In normal driving
with Mobil 1 -- I change them at about 8k. My Jag also holds 8.5Q -- Jag says 10K in normal driving.

If you do short trips you do need to change it more often, but even that depends on the spacing of longer trips in the mix and the outside temp.