They can be stopped all at once but are you sure this is a good idea? My protocol was to stay on the antibiotics for one year following the first negative sample after three negatives in a row. In my case, I had my first negative in June 2019. I was negative in July and August so I stayed on the antibiotics until June 2020 when my doctor told me I could stop. Your husband already has months of negative samples. The idea of staying on the antibiotics after 3 negative samples is to kill more bacteria that may not have shown up in the samples so that there's a better chance of having no reoccurrence.

If he is taking them daily perhaps he can drop to 3x a week? Or make some other adjustment without stopping completely until the year is up. In any case make sure the doctor agrees to stopping them before you do.