I noticed many people do it that way. Wouldn't you be overtraining your arms like that? Or do arms recuperate pretty fast? many others work their bis on the back day, and tris on the chest day (that's what i've been doing).
not everyone can "overtrain" their body. some bodies recover faster than others and can train more. like i can do arms every day off the week and never really be sore, and i still see results.
I will definitely work chest and biceps on a monday. Take a day off. Back and triceps on Wednesday. Extra stim never hurt me, just seemed to really shock my muscles.