I'm a huge fan of boosting gold vinyl's longevity by adding a cast gloss/luster overlaminate. cast obv.
best i've found spec's 5year outdoor, RTape VinylEFX being one. There's some expensive ones out there too that include real gold leaf, which I think would be pretty sweet & resist fading that much more.
Although, if it goes on a boat then I would add a high tack motorcross vinyl baselayer like Arlon 8000. 3 layers of vinyl, gonna get thick, but it should last. Did this for the chrome lettering I put on my parent's boat, even printed on the chrome before laminating. Still going strong now 3 years later, BUT its Lake Michigan