I think it was more than mere boredom. Lucy was a shrewd businesswoman, and as co-owner of Desilu, which reportedly was the sole investor in the show, I doubt that she would have run out on the production if it weren't for the fact that she didn't have the health and stamina required for eight shows a week. Her performance on The Ed Sullivan Show came on the night before she was due to return to the show after a two-week vacation. She had collapsed on stage in the middle of Act II at a Saturday evening performance in February of 1961 and Sheilah Hackett, Michael Kidd's assistant and later his wife, stepped in and finished the show as Wildcat Jackson. (On the original unedited Ed Sullivan Show clip, you could hear Lucy cough during the chit-chat with Sullivan after "Hey, Look Me Over.") Then, a few months later, another hiatus was announced, this one to last nine weeks to give the star more time to recover, but alas a few days later the decision was made to close the show for good.