Lets say I burn an engine about once a year, isn't it going to be faster to replace the engine in its entirety than to do a rotating rebuild on 3 or 4 of them?  This is assuming I can purchase whole engines to begin with.

 The shop can cycle rebuilds as the pistons and such are damaged but from a time-man hours perspective I feel it might be easier to just get a new engine and toss it in the frame, however there may be components I am not thinking of.

Lets say I burn an engine about once a year..
Which nobody has ever done.

If you start with an engine in good shape, use a good oil, keep it tuned.....I have no idea how you can burn through an engine each year.

When I built my cafe" engine I put in a bigger cam, Wiseco piston, ported head, Mikuni round slide carb, big foam air cleaner and better muffler.  Later I added a light flywheel when Armen started machining them.  Once I got it going I was happy with the results and I don't find a need for doing any additional modifications...it is smooth and relatively strong for what it is.

I didn't know how reliable the motor would be - so when I saw a chance to buy a complete 2006 motor with only a couple thousand miles on it for $600.....I bought it as a spare.  I built a stand for it, put in some fogging oil, and rotated the engine so both valves are closed, and now sits in the corner waiting for a day when it will be put into service.

My modified engine has 10,000 miles on it and it is still going strong.  When the Savage engine is taken care of it is capable of going more than 100,000 miles if you don't let the cam chain tensioner screw things up. And maybe if you were the type to go ride 80mph on the interstate on a continual basis it may reduce the life of the engine.  Abused engines run low on oil, low idle speed or on the wrong oil can be screwed up in only a few thousand miles - with proper maintenance I think it would be hard to ride the bike long or hard enough to go through an engine every 10 years!

If you have the money and a place to put a spare engine.......go ahead and buy one and have it ready just in case you need it.  Make sure the wiring for the two engines is compatible years so the wiring connectors are the same - and an engine swap can be done in a day.

What are you doing to these engines?

 I could scrap entire bikes and search for only 1995's but there aren't that many around unless I want to start shipping them in from out of state.  

"What are you doing to these engines?"

 One is running some modified pulleys at different RPMs at length, one I never bothered to put oil in.

"I've been following your posts. You don't do anything without analyzing the results.
What are you learning? "

 So far a 150/90 tire will not cause pulley squeal or damage parts but I have one more tire to wear out.

 The RPM's aren't conclusive as there's only 17,000 on the first pulley, we want to run 50k on each type.

 Correction, 25k of each type, 50k total.

Harley -Davidson  has sellers of after market engines readily available.

 Alright I will have it looked into, thanks.