A port can stay there for many months after it is not needed. Just make sure it gets flushed monthly. I had my port for a year after I was finished with my treatments. Since it needs to be surgically removed, I was in no rush to have the removal procedure done.
It sounds like your husband is doing very well with his recovery! Being able to work full time and do international travel is quite a significant improvement in only a few weeks post rads.
Best wishes with continued improvements with his recovery
