Age is usually quieter than a special effect.
Old prints and aging negatives change in uneven ways, but the most useful digital interpretation is restrained: slightly lifted blacks, gentler contrast, color drift, and texture that becomes visible only after you look for it.
Start with the Expired Color recipe on an image with simple light and a limited palette. Product color will not remain accurate, and strong modern neon can turn chaotic quickly, so use the intensity control as part of the look—not as an afterthought.