It is quite unfortunate that most coins were just punp and dump projects, and that is one of the reasons the prices of these coin does not come back after a dip, i think it is better to hold for at least 2 to 3 years to see the performance of some of them. As me, i like to hold for 4years before selling. However, holding for long time does not guarantee the rise of some of these coins but i give some trials to see how they perform.