On Mainframe Daddy's Retirement (Score 1)

I remember reading about mainframes going out the door, and after a certain point, and after my father retired, I started saying "his last job was to turn off the mainframes." He in turn, on hearing this story, would say, "that's just about right." But several years later, I discovered that mainframes and networked PCs co-existed in the same offices I worked in as a contractor. I was surprised to find these ancient beasts in place after place, But, they still do have their benefits. How much longer will they be useful?