... I had a question on activations. I know we get 10 per year - but if I have installed v13 a few times this year - thereby reducing my activation count - is there a separate "new" 10 activations for a new v14 upgrade purchase.
Yes. You get 10 restores per year per license. MC13 and MC14 are two different licenses.
Reason I ask is that I have been installing/reinstalling getting ready for Windows 7
You can extend the life of each restore by using the full 30 day trial period before restoring. Then use the Install Key you receive when you restore for the next 14 days.
Also - when exactly does the activation count roll over to a fresh 10? At the purchase anniversary date? Jan 1? When?
A year after it was used. If you use one on March 17, you get another one on March 17 the following year.
Finally - does one's activations stay "active" for an older version? Can't see why I would revert back to v13 - but if I buy v14 and install it...and use it for 6 months and then suddenly decide I need to go back to v13 - can I? Or do those activations run out eventually?
They are independant of each other. The new license doesn't cancel the old one.