I believe not - in fact he was on TV lst week advising how many thousand they've done, and he said he was there for all of them. In fact, combined with his time on 'Granada Reports' he is the most seen face on British TV. Yeah ... me too!
No, he hasn't. They record 20 episodes in a four-day block every four weeks, which gives him plenty of time for doing whatever else he does. Carol Vorderman may have missed a few in the very early days when Linda Barratt shared the numbers game duties.