Trading is very unpredictable and I think that its risky to do it but on the other hand it stays very profitable for a short term so due to that its also again worth it too.
You should know your trade is long or short.
Yes, longer can be more profit but i dont know it works on altcoin or not.
The risk will increase if u reject your analysis then dont adjust your SL.
In terms of profitability, I guess short term is more profitable because you can maximize your profit especially when you are good. Actually people chooses to be a day trader because they believe they can profitable with the volatile market of bitcoin or crypto currencies as a whole.
Also, I would recommend to have both short term and long term investment as that will give more opportunity to earn but always consider the amount you can afford only.