The major advantage of the color infrared film type is that it often tends to enhance subtle spectral differences associated with plant stress. Areas of stress that are readily apparent on color-infrared film are often so subtle on normal color film that the interpreter might miss them if only normal color images were available. In general, the film usually doesn't depict plant stress any sooner, just more vividly. In general, one simply cannot photograph heat. Films sense reflected energy.
Heat is emitted energy.
Our eyes can't see either type of energy. Film can sense the former, an electro-optical detection device is needed to sense the latter. In general, the colors appearing on a color infrared photograph have nothing to do with the thermal conditions of the objects appearing therein.