The varying seasons are not as unrealistic as one might think. Earth is rather unique in having one very large moon by comparison that keeps the planet on a stable axis. If a planet has no moon or multiple moons then it's much less likely to have a stable axis or tilt. It's the Earth's tilt that results in seasons. Stay tuned and you'll find out more about the moons in A Game of Thrones. Not sure if Martin really thought much about the physics of it all, but the idea is plausible. The lack of stable seasons wouldn't have anything to do with the planet's orbit around it's star. Therefore, it would still have years in the traditional sense..., ie, how many days it takes a planet to orbit it's star. changing the tilt would change the intensity of the seasons, but they would still all happen within a year and be the same length, so no not really. At all times half the earth is light and half the earth is dark, during summer for the northern hemisphere the light/dark plane is perpendicular to the tilt axis projected onto the plane of revolution so the northern hemisphere spends more time on the light side than the dark side, during the middle of spring/fall its still tilted the same but the light/dark plane and the tilt axis's projection onto the revolution plane are parallel so the tilt doesn't matter since even with the tilt each point on the earth spends the same amount of time in light and in dark, and then during the winter the northern hemisphere spends more time on the dark side. All of this would still be true if you increase the tilt. 3D pictures would really help to illustrate this but I don't really feel like making some.
