Eric,
Gregory's comments are right on the mark. I will add that with proper care, a good oiling/cooling sysytem and proper build, you can have an engine that will last a long time. The important thing is to get a quality built engine in the first place... there are no cheap shortcuts. My engine is not all that special in terms of power or looks. It does meet my goal of have adequate power with reasonable reliability. For the particulars look under 'dubudeee' in photos. The important thing is quality parts that mesh with the overall goal and that work in harmony.... meaning right cam, carbs, exhaust, heads, etc.
Most owners put less than 2-4,000 miles a year on their Speedster Replica. Me? I've put on around 8,000 miles a year. Point is... with care, at 4,000 miles a year, you can run 6-8 years with no major breaks. That's an eon in our little Speedster Replica world.
I have approx. 20,000 miles on my VS. I purchased it in August 2001. It has a non-factory 1776cc engine. You can purchse something similar from CB Performance through either JPS or VS.
Next week at this time I will be 300 miles into a 3500 mile round trip to our Site Club (Speedster Owners. Com - SOC) rally in SoCal. I feel confident that my engine will carry me both ways.
Hope this helps. Write if you have Qs.
Jim