The two main determinants are the gravel base and proper compaction. We suggest 12 to 18 inches of compacted gravel. In Maine we experience frost heaves. Without a solid foundation on which to lay the asphalt mix we cannot determine the outcome frost will produce. Compaction, compaction, compaction! Compaction is the leading cause of asphalt failure. (I.e. shrinkage, cracking, water problems, premature deterioration. We have a 1-ton, 3-5 ton, and a 10-ton roller.