The length of time you should expect your tint to last before needing to be redone actually depends on several factors:
The type of film used. Simple dyed film, while very cheap, may only last a year or two. Hybrid film which contains both dying and reflective metals lasts four to five years. Very expensive window film, made in a vacuum chamber, can last as long as a decade. You should consider how long you plan on keeping the video when choosing what window film to buy. Also, some hybrid films can interfere with your cell reception because of the amount of metal in them.
The quality of the installation. A good professional installation will generally last longer than do it yourself.
Your local climate. Window tint generally lasts longer in cooler and cloudier areas. If you live in the desert then the constant sun exposure will reduce the lifespan of your tint. You should talk to your installer or other people who live in your area to find out what to expect. As tint is applied to the inside of the window, it is not affected by rain or snow.