How much sun (UV) exposure has your OEM paint been subjected to in those five (5) years? I would guess it is minimal with the vehicle spending much time in a shed away from sunlight
Experiments I have conducted have proven otherwise...Alkyd Enamel chemistry based paint has poor uv sunlight resistance & fades significantly with UV exposure.....
Why one would go through the extreme efforts of sandblasting/preparation required to properly prepare a vehicle for paint & use a low quality paint is beyond me.....I suppose it is a cost issue....If that is the case, I would skimp on the tires.
Overall, it is the restorer"s vehicle end use as a goal in paint choice.