You can probably make either way work.  If you are taking the machine to a dealer and having the work all done at ~$75-100 per hour, it may lean toward the exchange.  If you have someone who works on it at your place at a lower cost, then I am led to believe that the Axials can basically be rebuilt indefinitely at a lower cost then replacing.  My personal experience with them is zero, but have friends who have a herd of them, some of which have to be in the 5000+ hour territory by now.  From seeing their Axials in the shop, it looks to me like a complete rebuild on one of them is a little different from doing the same thing on a conventional, because on the axial you basically replace all the wear parts...the conventional, even after rebuild, has a lot of parts which remain worn out. 

I think there is some fallacy in the reasoning that you can take the maintenance budget to put  toward trading, because the replacement machine is still going to be used and is still going to require a similar maintenance budget.