The influence of the exposure time in the initial state at room temperature, which is comparable to the time of operation in orbit (5, 8, and 10 years), on the mechanical properties of polyimide films of the kapton H type of different thicknesses and manufacturers under tensile conditions at room temperature was studied. A change in all studied characteristics (forced elasticity limit, fracture stress, total deformation before fracture, contributions of individual strain components to it, modules of elasticity, and forced elasticity at individual stages of deformation) was revealed. The changes were different for amorphous and partially crystalline films, as well as for amorphous films of the same thickness, but obtained by different manufacturers.