From my experience, it is profitable. I prefer short term than long term though in some instances I am forced to hold when prices don't go my way. My technique is that when the current price of altcoin is below by 10% its average price, I buy and then when prices go back to its average value I sell. I don't mind making many 5% trades per day.
Actually I've try trading twice.
And thankfully it both give me a good profit by then.
I tried to trade bitcoin and ethereum. In comparing this two coin, bitcoin can give higher income than ethereum.
But im not saying that ethereum is not a nice coin it also a good coin.
But in terms of the income that it can bring back to you , I will go with the bitcoin.
Its nice to do trading , you'll just need to take some risk sometimes.