I have always just followed the book: 5k intervals for oil changes on the Airheads and 6k intervals for the Oil- and Hexheads. Never had an oil related failure, and I'm at 600,000 BMW boxer twin miles.
That said, when I ride my 1928 BMW in the Cannonball (see my sig) next month, I intend on changing oil every night, which is roughly half the 600 mile interval the maker recommended. In this case, I hope that, if there is a problem, I can find out about it before I am stranded on the road...