Many professional bodybuilders recommend stopping just short of full extension in order to "maintain the stress" on your biceps.
I contend that you are not only shortchanging yourself, but you are also putting yourself at risk of long-term harm.
The biceps tendon plays an important role in pec strains and rips. Not only are you not receiving as much hypertrophy benefit (working through full-ROM is nearly always greater), but you're also not strengthening your tendons across their whole range of motion.
This is an incline dumbbell curl, and I recommend doing it 1-2 times a week to not only increase strength but also to help prevent injuries. I prefer to perform 3-4 sets of 8-12 reps.
https://www.youtube.com/watch?v=bPQN2tfS_sE