I think a day off every couple weeks is fine. That would mean a field player would be in the 149-150 game range. Catching should be split roughly 60-40.
On this year's team, Yoshida seems to have problems playing 6-7 games a week. His slow streaks have happened when he plays more than that. We can complain about it all we want, but the data says he does. It's probably a cultural thing; not sure how Japanese schedules work. One thing for sure is the Japanese teams never switch time zones.
As notin said, you have to give the bench guys some playing time; else, when needed, they are going to be worthless.