The truth is that it is quite possible, even likely, that they are not. Printing is an inexact art. If your lab allows you to examine your prints before paying for them, then by all means do so. Most machine-printed photos have the settings printed on the back and can easily be corrected. The only way to really tell who's at fault for a bad photo is to examine that negative, THAT'S the original.
Film is a permanent record.
Slide films will last longer. Slide films that are properly E-6 processed should last 25 years without fading. Kodak's Kodachrome slide films have proved to last a half-century and more and still keep their vivid colors. Properly processed and stored black and white films and prints last the longest. Part of the problem has been the demand for rapid processing systems, leading to shortcuts in the developing process.