"Normal" is hard to say. Does it happen? Yes. Can it get in the way of healing? Yes. But it really has to be his decision. Hopefully therapy can help him figure out why he continues to see them and if it is healthy for him. Once he understands the why, he will have a better idea of if it is something that is wise to continue. It will have to be a decision he comes to on his own. Changes that are made under external pressure don't tend to stick. I'd voice the concern to him once, but then after that let him know that you support him and believe in his ability to come to his own decisions.
Hope that helps.
Like a spent gladiator
crawling in the colosseum dust
who can count on his remaining limbs
all the people he can trust.
Like the one who stands behind him
cheering him on
Estatic when he stands defiant,
wild with abandon when he's gone
just stay alive.
do whatever you need to.
you are worth it.