Honestly it depends how hard you drive it...
If you're doing twisty cruises and hills runs... Full Comp right away...
If you're driving it twice a week to go to your mums place for tea, I'd stay on 3rd party fire THEFT until you can afford it.
Also, if you've got the money sitting in your account, you just don't Want to spend it... then go Full Comp.
Oh Noes, Moh got Moh'd...
Googling for Skyline GTST Blank Key doesn't actually come up with any images of the key that I've got with mine Black plastic with an S imprinted in it.
Mine:
Mohsen's new one:
Does my one have a separate part number, Mike?