My understanding, from a good friend of mine in Florida who wraps cars for a living, is that the wrap can last anywhere between 3-7 years depending on the quality of wrap you're purchasing. They can't really guarantee the life span of a wrap because conditions are different for each application. He said they usually last 2-3 years in Florida's sun before they really need to be removed from discoloration. You're not supposed to treat the wrap in any way, with wax or sealants- IIRC, all sealants or waxes should be removed from paint prior to wrapping the vehicle for best surface adhesion. Many people swear it doesn't damage the paint, but often times people will find it pulls clear coat or etches the clear with time.
When I pulled the wrap off my GTI, that had been wrapped for a little over a year in Florida, it pulled off clear in some areas, pulled up paint chips that had been filled, pulled paint in some areas entirely, and was fine in other areas.
Overall, save your money.... huge waste and looks like crap, even when you do use quality wrap.