My deepest condolences to your husband. I agree with what everyone else said, and add that although there are unhealthy levels of grieving, it doesn't sound as if your husband is at that point.

I've seen it--my ex, more than a year after losing his mother, used to deliberately play clusters of old Southern Gospel songs about somebody's dead saintly mother who's up in Heaven now, and sit there and cry all afternoon. He and his sisters already had their minds made up that "This year, Christmas is going to suck, now that Mama's gone," and then with their attitudes made sure it did. I think they sometimes acted as if they were the only people in the world ever to lose their mother. And it wasn't only her. Every holiday, and on everybody's birthday, they'd make their rounds visiting the cemeteries, and stand there at the graveside of someone who died upwards of fifteen or twenty years ago, wailing and sobbing as if it just happened last week.

This said, an anniversary or something like a milestone birthday ("Mama would have been 70 today....") can bring it all back and trigger a temporary bout with tears. This is normal, even decades later. I know, I lost my youngest child 26 years ago, and every year on the anniversary of when it happened, I have a dip in my depression level. It's when people stay obsessively stuck in it, like my ex and his family did, that I don't think it's healthy. I will never "forget" my daughter, and I will never "get over it." But I don't have to sit around playing songs about dead children, and fixate on it.