I think the key qualifier is whether the NH can hold the same equipment in a different base. If you are a NYC7ERB but want to do SEA73NB and on that AE (12 months and 1 day after the NH's start date) the NH could have been awarded SEA7ERB, the NH is not eligible to be awarded SEA73NB, regardless if more than 12 months (but not 24 months) has passed since starting.