28 months vs 31 months of ADT is unlikely to make a difference.
Although my case isn't identical to your husband's, the original recommendation for me was 24 months of Lupron. This was changed later on to 18 months, based on a (Canadian) presentation that got a lot of press at an ASTRO mtg (I think). I didn't mind the change at all.
I would highly recommend that your husband gets a DEXA scan in six months as a follow up to the result from 1.5 years ago. And I hope that he will continue to exercise as before. Good job; it should get easier once the effects of the ADT wear off and his testosterone level starts to rise.
PS: My RO did a PSA test 6 months after discontinuation of the ADT. Hence, your husband's schedule may well be the norm.