'Evia' island can satisfy all kinds of preferences regarding vacations, from lovely beaches to unexplored mountain-routes through amazing forests and beautiful waterfalls. I strongly recommend a, more or less, 3 hours drive through a forest-road (from 'Feneo' to 'Zarouhla') where the scenery is really breathtaking. You should use a motorcycle or your mountain-bike. Leave your car at home, it's useless for this kind of roads.
At Evia island getting boring is not an alternative because you have many choices to go to and spend your day. The distances are not that long and you have the opportunity to pass through tiny villages where you can stop and take a swim (in some of them anyway), eat good and cheap food and then go back to where you have started. Evia is considered to be a 12-months island but if you ask me I think the best season to go there is May, June and September (because its less crowded).