I think that long-term investments take 5 years or more. Not every crypto investor will be able to keep their investments for so long. I'm for short-term investing.
Long-term investment doesn't have any fixed definition. It could be for 5 years or it could be like 1-2 years or maybe 10 years+, all depends upon the market conception of investors. Considering any investment to be long-term or short-term is subjective matter. I may consider day-trading to be short term and holding for 1 year to be long-term.