It was unusual to be called for cross examination as a single joint expert witness, and it would have been all the more unusual to be in court for the cross-examination of a Single Joint Expert (though I was not the SJE in the case I did attend) twice in a month.
In the case I did attend, I was disputing certain aspects of the SJE's evidence, which was not a role I was aware of until I ended up occupying it. I would be comfortable to occupy it again.
I am relatively unusual amongst expert witnesses in being willing to accept SJE instructions, which can be problematic. I can see why some experts might be concerned about the great care needed in communications when accepting instructions from two parties who may disagree with each other at the level of disputing the interpretation of the court's instructions they wish you to take!