i think it would do alot of people some good to just go ahead and get your oil analyzed by an oil lab like Blackstone.

they will be able to give you a very educated opinion on how far you can take your oil change or if you need to pull back. for the few dollars it costs to do the test it may save you alot in the end with the information you'll gain -- either because you're saving engine wear or money by not having to change your oil as much.