Like everyone else said above, use high performance, intermediate vinyls are poured and stretched so they always want to shrink back to their original size. About a year from now you will see a visible adhesive outline around the letters where the vinyl has shrunk and that outline will collect dirt and look ugly. Often times this is why they peel, cause they are shrinking and loosing adhesive around the edges. High performance vinyls are poured (no stretching) so no shrinking, I like to use Oracal 951, if you look at the actual vinyl bulletins (which are readily available where you purchase online) you will see only black and whites are rated the longest, so I choose to go with the best and feel good about what I'm putting out there. I love seeing stuff come back 10 years later looking good, faded and ready for a refresh, scratched up but no peeling, shrinking, etc, important note, they come back!
To answer on how to make it easy for installers, like said above print, laminate, and contour cut together, or cut everything out of the vinyl, get the flame printed, and apply the flame to the space where the flame was cut out on the vinyl. You can use a stabilo or crayon lightly over the cut marks in the vinyl backer to show where to place. Then transfer tape them together and you have a one piece install. It's definitely worth doing as much in the shop as possible as it is always harder in the field and the labor rate usually much higher as well, plan ahead, save later headaches.
I forgot to mention above, printed products are rated for 3 - 5 years before significant fading with the UV exposure you would expect on vehicle lettering, maybe a little longer when laminated. Depending on your client's expectations sometimes it makes sense to use a combination of colored vinyl and prints for best long term results.
