Best duration touch-up paint

[Stockholm VW]

I’ve use PaintScratch brand touch-up for the last four years. Lately I have noticed that, although great and glossy at first, the chips I’ve painted L456 Rubin Rot (Ruby Red)no longer keep the glossy surface. After about a year it seems the “clear coat” turns into flat. It looks like crap and looks like I used a flat paint to touch things up. Most probably won’t notice, but I see it every time I approach the bug.
Anyone have any experience with the PaintScratch brand. If not, what brands are you happy with? Which ones last???

Thanks in advance, Wizards.
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1966 Volkswagen 1300 Sedan, 1641 cm³, 12 volt conversion, L456 Ruby Red, Platinum leatherette.