I have recently switched from Humira to Remicade because Humira was no longer effective. I did get 3 good years of remission on it though. One thing to think about
before switching is that switching back is often not effective, meaning that if he decides that Humira is not working as well, there is a good chance that Remicade will not be effective if he goes back on it after a long time off. This is something to keep in mind, and would be reason enough for me to stay on a biologic that is effective. That way he has Humira on reserve if the day ever comes that Remicade is no longer working for him.
I am currently on Remicade and 6MP, because like COT said, it has been shown that the 2 together decrease the liklihood of developing antibodies. However, that being said, I just had an appointment with a doctor at the Cleveland Clinic, and he said that this is only true if you are on the maximum allowed dose of an immune-suppressant (I am currently on 50mg, which he called a "baby dose" and said that it would not be effective and the risks would outweigh the benefits). I will have to discuss this further with my GI, but something to keep in mind if your son does decide to switch to Remicade.