@Kristen *******
there is no age limit on who can get the "trailing spouse" Non-O visa or matching extension because they are married to someone on a 'retirement visa'.
SOME offices try to switch the spouse off the trailing spouse matching extension once they turn 50 but there is no rule that says you have to get your own visa. I know a couple in their late 70's one on a retirement extension and one on a trailing spouse for many years now.
You just can't get that initial 90 day Non-O inside the country because trailing spouse Non-O's for people married to retirement visa holders are not issued in country