The UV will fade the paint over time, but the foam will hold together for quite a bit longer. EPS is surprsingly durable stuff.

Replacing it every year is excessive, even the helmet companies only recommend replacing it every three years and they HAVE to be paranoid because if a single helmet out of the gazillions they make every year fails due to just plain wearing out, their reputations are pretty much in the gutter.

If it's less than a year old, doesn't have any cracks or big holes in it, you should be in good shape.

If you just don't like that helmet anymore and you just wanted a new one, well, that is what it is.