Hi Gary,
Very prudent and sensible advice. My procedure isn't quite as deep as yours, but similar in approach and then again I have lighter requirements. I have Snow Leopard on one drive and Mavericks on another. Then I have an external 4TB G-Tech split into two partitions for clones of the two operating systems. I use Bombich Software's Carbon Copy Cloner to up-date the clones every day that anything significant is added to the system, be it software or documents. Like you, I adopt a conservative approach to system upgrading. I am not an early adopter, in fact only do it when some piece of software or other requires it. This is based on the leave well enough alone philosophy, but if you buy a camera which needs LR5 to demosaic the raw file and LR can't operate on Snow Leopard, bingo, upgrading becomes a necessary part of progress. Anyhow, I'm pleased to report that I have had ZERO problems operating all the usual stuff in Mavericks - the Adobe Suite, Lightroom, the Epson 4900, SilverFast, LSI PrinTao, etc. etc.