Completely depend on the coin we choose because some coin will show their potential in a short period of time, but we need to have patience in this altcoin market. If you cannot sell them for higher prices suddenly the prices of the coin will drop that's why we need to be very active in the market.
People divided in two groups.
1.Technical Analyze working
2.Technical Analyze not working
I am in both sides. With following technical analyses, you can not be on profit. BTC mostly does not listen technical analyses.
By the way with good studied technical analyses you can guess what to do when a price of a coin come to certain point. You determine your points earlier and do what you planned to do when the price come to your analyzed level.
Basically, resistance and Fibonacci levels are good points for selling the coin.
Can it go higher after you sell? Sure.
But there is no limit and you must determine the limit for protecting your profits and control your losses.