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there are coins that can be maintained 1 year to 5 years, it all depends on the road map. but not all coins can be maintained for a very long time. I think the coin that you hold (NEM) can still be maintained because for now it still has a price in the market and there are still many NEM enthusiasts, and that allows NEM to ATH
From that perspectives, only coins that have good development can survive with that long period, maybe NEM still exist but the competition inside the market is really high, without continues updates new projects will beat you and overthrown you to the point that interest coming from investors will be push away. It's hard for every developers but if they are serious in taking the challenged, they will not allow things like this to happen, Bitcoin and ETH still have that huge capabilities to stay strong and still keep the tops spot in terms of long-term investment.