It would be financially beneficial for him to reapply because his benefits would be increased and if he dies before you do your survivor benefits would be increased.
As he continues to work his current work record is added to his earlier record and his benefit should be recalculated every year. The change will be likely be minor because each additional year only contributes to a total work record of 35 years. A high earnings year, however, would displace a low earnings year because your benefit is based on your BEST 35 years of earnings.
The hard part here will be to repay all those months of $1,900 in benefits. While the numbers show significant benefits few people take advantage of this option because few retirees actually have the money. A better option is to simply defer taking the benefits.
Scott