Long term holding, and other portfolio strategies, can be a smart thing if you're properly diversified in your crypto portfolio. Diversification is pretty much the only hedge against market fluctuations where you can assert some control over them, and even then, is no proven smoking gun when it comes to the duration any asset should be held in a portfolio for.

The duration a crypto asset should be held for is proportionately related to how risk averse you are as a crypto investor. Another way of putting it would be, how much risk are you willing to accept by holding a certain crypto asset for a certain duration of time?? Risk of course being defined by monetary gains and loses in the crypto asset being analyzed here. ie, how much are you willing to lose or gain??

If the answer is, I like risk, then you are a non-risk averse investor and you should hold on to whichever asset your OP is inquiring about for whatever you deem a "long time holding" a certain crypto asset is. But if the answer is, I don't like risk at all, then your a risk averse crypto investor and you should only hold the crypto asset you have in mind for whatever duration of time you deem "short" for. If the answer of how risk averse you are falls somewhere in the middle then the answer of duration is directly proportionate to how far towards one end or the other of the risk spectrum that your particular version of being risk avers falls towards. Simple really