signal should we need until whenever. because the signal can anticipate us if the market starts to fluctuate up or down. so in trading you must be good at doing analysis to determine the right time for us to move to a good position
As you shared, the signal gives us 2 options to buy or not (if you don't have it), we also rely on the signal to hold or sell 
I don't think it's necessary with those types of signals, because it's simple and easy to see, only we can make it complicated and confusing. It's just instinct after years of entering this market after the bad news keeps happening, and a bear cycle lasts long enough then we will move on to another cycle and if we understand the basics then It is entirely possible to get x100 profits in just long enough to end that bull cycle.