Seeing as how it's essentially a Sportster engine and they are well known to go 100,000+ I would expect quite a few. The Buell engine is considerably "hotter" (which does affect longevity) so I would rekon a well cared for (not abused) engine would make it to 75,000 or so. I haven't really found a whole lot of high mileage Buells though. Most people don't rack up miles on a sporty bike like the Buell like they would on a cruiser.
One good thing though is rebuild stuff can be had readily and cheaply because of the Sportster heritage.[cool]
Just change your oil every 3-5000mi with whatever brand you want. There is no "magic oil" that will add another 100,000mi of life, no matter what the marketing people tell you. Just use a quality name brand and change it at the recommended intervals. Staying on top of the maintenence is key to keeping a bike going a long time.
