I used to work for a tint shop, and do NOT recommend 3M products for Tint.turns to crap in no time.I would stick with Solar gaurd or Llumar... I have llumar 15% all around on my car, its not TOO dark and of course not light at all
I can see at night just fine, and it isn't ghetto by being like Limo.
there is some stuff by Solar gaurd called "quantum" and it is a pretty nice film... will never fade, any film that has metal in it won't fade....film that is dyed will fade over time.
so your mirror tints will not fade (depending on who makes them).
but from my experience, I say go with llumar

llumar and solar gaurd have lifetime warranties. not from fading...but from the film coming apart or bubbeling (depending if is a good job to begin with.. if who ever installed it did a crappy job.. the shop should fix it...and DON'T be afraid to bring the tint job back if you're not happy with it.. they will more than likely fix it)
my 2 pennies
-Dan