Coppercoat loses its effectiveness over time, it is not a lifetime solution. May be this is why conventional antifoul has been applied.
However, I think the real question is whether underneath the coppercoat she has been gel-shielded? And then, how many coats of gel shield have been applied?
Gelshield comes in two colours and successive coats are applied in a different colour so that you can work out how many layers are applied. If she has four coats of gelshield, that is good for 10 years of protection, and therefore you have 2 years left on a 2015 hull. If less than 4 coats, then you need to strip it all off and re-shield now it anyway.
You can go longer than 10 years, but you risk moisture ingress into the laminates the longer you leave it. The choice is yours.