I think this is also valid to non-asian music as well. Well, if the group still continue to produce good music, I think that's what matters. I don't listen to groups thinking about their members. When it comes to boy bands, it usually won't make much of a difference when a member leaves. Generally the member who leaves is actually the one who's really out of place or that doesn't contribute much to the groups music anyways
Though there are definitely a few exceptions.