I agree with both Needsize and Debaser.
The bicep constitutes only 1/50 of your total body mass. Thats pretty small and the Bi`s get worked damn hard when doing chins, rows, etc.
IMHO..... aside from the anterior (front) delts, it is probably the most overworked bodypart.
I do relatively very little direct bicep work. 3 sets max.
But half the times I only do one set but it is a rest pause set and I smoke the shit out of them or only 1 set of up and down the dumbell rack with no rest in between ( a total scorcher ). Lemme tell ya, I look real silly when I worked back down the rack and curling with measly 20 lb. dumbells and it takes every ounce of strength I have to get 6 reps and my face looks like a watermelon ready to explode but oooooh the pump and the pain.
Try different things. Shake things up every now and then.