Looks like I spoke too soon.Forever, you say..... is that a guarantee, or purely an opinion.
Told you the inside sticking ones are betterRR, you are a doomed man. Another one in the post tomorrow. Maybe two.
It goes without saying that the surface you stick these on to should be entirely grease free (or indeed any wax or rain-x or other stuff you may have put on the car previously), and it would be best to use a proper de-greaser first (ether or trike or similar).
Not that I'm saying you didn't RR, just for others. We all know that on yours it'll be overspray.