This article presents a new continuous-time model for long-term scheduling of a gas engine power plant with parallel units. Gas engines are shutdown according to a regular maintenance plan that limits the number of hours spent online. To minimize salary expenditure with skilled labor, a single maintenance team (shared by the gas engines) is considered which is unavailable during certain periods of time. Other challenging constraints involve constant minimum and variable maximum power demands. The objective is to maximize the revenue from electricity sales assuming seasonal variations in electricity pricing, by reducing idle times and shutdowns in high tariff periods. By first * Corresponding author. Tel.: +351-210924643. E-mail: pedro.castro@lneg.pt 2 developing a generalized disjunctive programming model and then applying both big-M and hull reformulation techniques, we reduce the burden of finding the appropriate set of mixed-integer linear constraints. We then show through the solution of a real life problem that the most efficient model involves a big-M reformulation of the set of disjunctive constraints, while gaining valuable insights about the system.