For lot of traders the words “Trend Is Your Friend” means a lot and they follow them and make lot of them.
Okay so we draw trendlines to help us know if the trend is going to break.
Where do you draw the trendline and how many times you re-draw it is up to you, not every trend is going to be able to draw a good trendline, every trend is unique, just like how many of us in this world is unique that is how trends are.
So in conjunction with trendlines you should probably be looking into reading price action, charts etc. to have a better understanding at WHEN and WHERE to use this indicator.
Trend lines are the most powerful tool for trend and reversals. Just add an ema for more confirmation you’d be surprised how price action acts against the lines and will help you decipher your next trading decision. Keep in mind that lower time frames have a lot of noise and can give you false alarms. In my opinion using the daily and weekly charts give a broader spectrum of price action and more likely where it will hit next. Happy trading 
It is an option using trend line, not a must. Nial Fuller don’t use trend lines and yet his method of trading is quite effective.
We all know that trend line is a very important for technical analysis. And i use it with big time frame for more accurate result.