Diesel Engines are usually built of higher quality and are usually outlasting of gasoline engines.
Some diesel engines can last from 500,000 to 1 million miles or even more before needing rebuilt.
Some semi trucks have engines in them with over 1 million miles and they're still going strong even with the same engine.
With proper maintenance the diesel engine should last at least 500,000 to 1 million miles.
Typically a diesel engine will easily outlast a gasoline engine of the same size.
My friend has a diesel pickup truck with 1 million miles on it and the original diesel engine is in the truck so they can last a really long time.