Analysis of information sources in references of the Wikipedia article "Skylab" in English language version.
The Skylab 3 crew launched with a 28-day supply of formulated nutrient-defined, high-density food bars which enabled the extension of their flight from the planned 56-day mission to 84 days.
Three crews, launched atop Saturn 1Bs, would visit the space station for visits of 28 days for the first crew and 56 days each for the final two crews.
At the time the Skylab 4 crew departed, one CMG had already failed and another showed signs of impending failure.