I can decide to buy any coin and hold it for as long as I want as long as Im very sure that it has the potential to go further. There are good altcoins in the market that one can invest and hold for long-term just like XLM, NEO and Zcash. These coins do have a good potential and investing on them for long-term will be worth it. You can also trade a few hours everyday and make good profit daily, you can make 5% from $100.
Yes that's right, buy the coins that you believe on their future because if you are just basing on the hype of the people, you will just lose money because of that irresponsible investing/trading. Its good if you make 5% everyday, this only mean that you're a good trader. 
more time we hold coins, more chance for us to earn huge profits.mostly coins developtment need long time.and when it completely developted price will rise alot.
This will depend on the coin you are holding because not all coins are doing good in the long term, some of the coins are dying because they can't take the competition anymore. Its better for me to hold the established or the top coins in long term than to hold shitcoins which will never make money for me.