@S**
I think you might be confusing things.
The year-long, multi-entry Non-O visa doesn't let you stay IN thailand, it lets you apply to get in for a specific number of days. (in the case of a non-O visa 90 days each entry). It's the 90 day entry stamp that lets you stay IN thailand.
AND
if you bounce out and back in just before the expiration date on the non-O VISA itself you'll get a final 90 days (that lets you stay in thialand PAST the expiration date of the visa).
You can apply for a 60 day visit family extension on ANY of those 90 day entries when you have 30 days or less left on the entry stamp. (NOTHING to do with the validity of the visa itself at all)