usually I charge my mobile when its reach 20% until its comes to 100% but I read out an article it's not good to charge for an long time until its comes to 100 it will reduce the battery performance it's better to remove at 80%
Charging beyong 80 stresses the battery and would sometimes overheat it. It's better to plug in at 20% uptill 80% this would last the battery 3 times more than the normal lifespan since it would not use 1 full battery cycle either.. If this is followed the battery wearout would be 0.22 cycles per charge.
Also make sure to re calibrate the battery once a month that means draining it down fully till battery is 0% then charging it back to 100% this would ensure the health of the battery.