Can my husband apply for a follow visa despite turning 50 soon?

Hello-

I got my O-A multiple entry based on over 50 yrs

My husband is 49and received a O visa multiple entry and is required to report at border every 90 days.

We understand that he is able to apply for a “follow” visa and as a dependent, then he will not have to report at border / do visa run.

We are in Thailand now for 3 months and just returned from visa run and reported again to immigration. He will turn 50 end of November.

Question- if we apply for the follow visa for him, will this visa be valid even though he turns 50 at end of year? Or will he have to apply for O-A as he will be 50 years old and he is no longer eligible to hold a follow visa? Thanks for your insights!