Today's biggest issue is filtration. Don't skimp on the filters (never even look at a Fram). If you use a quality synthetic, you can go a really long time on your oil, provided it is kept clean.
My examples for a 5k filter change interval and a 20k oil drain interval:
1997 Ford E150 with a 5.4: Lost it to the ex in a divorce at 302,000 miles. Always used Motorcraft filters. No oil-related failures.
2003 Dodge Sprinter with a Mercedes OM647 2.7l turbo diesel: Currently at 372,000 miles. Just did the 20,000 mile oil change over the weekend, an the oil still felt great. As for the filters? I have been getting a generic "Premium Guard" filters, made in Korea like the OEM filter, and there is no discernible difference (cartridges, not spin-on). I'll be sending off for an oil analysis at 390,000 miles when its oil is changed again.