Also depending on your weight, arm length, built etc. their will always be a limitation and you should avoid comparisons.
I have been training hardcore for many years, played college football where I trained like an animal, now I compete in amateur fighting bouts, and I still struggle to get 12.
Ive seen kids that never did shit in their life bang out 20. Overall my point is keep some record of your progress so you can keep challenging yourself. Also try adding some minimal weight, like 10- 15 lb. db's and go for 5 lets say and try and increase in that regard. I find constantly just challenging myself in reps gets boring and unproductive after awhile.
Good luck seems like your on a good track, and I would advise you to rest it like any other exercise/muscle group (i.e 2-3 days in betweem) and keep the progression and intensity high