I don't have arms together; they are split between bi, tri, and forarms. My workout cycle is 4 days, so everything is hit every four days.
For those who do bench work on different days as arms, yeah, maybe once a week.
Here's my split:
day 1 - chest/tri/forarms/abs
day 2 - delts/legs
day 3 - back/bi/forarms/abs
day 4 - rest
This way there isn't any overlapping. Also, forarms and abs have a faster recovery than other body parts; this takes advantage of this.