Liquid loading is a common problem for most of the mature gas wells. Over years, many methods have been developed to solve this problem. One of the widely used methods is plunger lift, which requires shut-in of the gas well for a period of time. Then, the well is reopened, and it is expected that the natural energy of the well will push the plunger to the surface carrying the liquid with it. Optimization of the plunger lift requires that the well be shut-in for a period of time as short as possible, followed by production of gas for as long as possible. This note examines the requirement for a successful shut-in of a well so that the well can sustain the production for a longer time. The note also discusses the condition under which the well will not sustain the production and the plunger lift will not be effective. The analysis is confirmed with several field examples, which will be shown in this note.