Yes you are right long term investment is more and more favorable in contrast with short term but remember that some users know very well about short term coin and have hold on it so they can easily make cash in this way. Long term investment can lower the chances of your defeat and may be due to this reason you make certain good income. Altcoins investment is good if you hold it for lengthy time in contrast with sell it at the same day.
For me, when I buy a coin, I have to be prepared to hold it. The word "long term" must have different meanings among us. 1 month? 1 year? 5 or 10 years? Or how strong we hold it, or also the profit target we want.
I think when we really know what's going to happen to the coins we have, we'll be even more confident to hold them. Here we need not only profit calculations, but also confidence in our own analysis.