'Wasted Years' was the first single from the album, and is one of Maiden's most accessible and mainstream-sounding songs. It is probably about as close as they can get to the mainstream and still retain their unique Maiden sound. There is a long and very melodic chorus by Maiden standards, and an excellent instrumental and guitar solos.
It seems to be some sort of an admonition to appreciate the present and not take things for granted. It could also be a reflection on the World Slavery Tour, that really burned out the musicians of Iron Maiden to the point that a split of the band was feared at the time. It's obvious, though, that all that time was certainly not wasted, and that those were indeed Maiden's "Golden Years".