I really think COSS will be worth holding that long. Eth and BTC don't have that much room left to grow, so I feel like the smaller market cap coins with a promising future are the way to go.
COSS pays dividends based on 50% of the fees it collects on the site. If you think that Binance got to be the #1 exchange in under a year, it's a no brainer that COSS is a good long hold. They've really been putting a lot of work into making the exchange better lately. It really shows.
Depending on your choice, if you choose the right Altcoin potential then in the future their high potential is quite high. But if you choose the wrong ICO project would be a mistake to lose capital. So I recommend learning how to analyze in the market.