Well, to speak frankly, there are so many altcoins such as: ethereum, ripple, litecoin, dash, nem,..and so on. I wonder how long you will get marry and how long you will hold coins. Because as you know crypto market require a little bit more risks, especially when you hold for so long time. I offer you to hold ethereum and litecoin. I suppose you somehow should hold more than one coin, if you just hold one, its considerbly dangerous, probably you may get nothing for marrying from crypto guy. Ethereum is having a big potential till now, I profoundly support you to hold it. Besides, youd better to diversify coins, litecoin or dash is also a case point. Anyway, how long you can hold for earning with a significant benefit, it really depends much on your skill, experience,knowledge, and patience and a little luck.