I preferred a long term investment, slowly but surely!
but there is also a danger that you will choose a coin for a long-term investment and you will lose all of your money that you have invested slowly but surely!
That is why you have to hold at least 15-20 tokens and Bitcoin. Trade them using both ways. Some altcoins should be held, and the others might be exchanged.
I does not matter as long as you are an investing for earning. It depends on the type of crypto currency you want to invest in. If you are planning to go for Bitcoin or ETH, keep your plans long and tall for only holding the said coins for long can bear some good money. About crypto like NEO or ripple, I would say you can have a short term investment to earn quick money and now is the best time to do that because the value of Bitcoin is on the rise.