too many interviews!

I have got a job offer recently and the H1B process has started.

Today another interview is being offer. This is the second time that I got interview invitation after I got my first offer. I am interested in today's interview position is that it is pretty sure that they will take care of my GC.

However, since I have accepted an offer, should I ignore this opportunity or accumulate more experience.

How will you guys deal with this situation after you have already have an offer in hand?