I tend to have my RB slider between 35 and 40. I don't want a guy going over 20 carries per game and look to have a 'committee' approach with 3 or 4 RB'S who can catch too.
The 'lead back' often disappears in the 3rd quarter but generally comes back fresh in the 4th quarter - which is what I want. #FinishStrong
Another point to remember is that on some 2 back sets the player in the second RB spot may be FB1. So you need either an RB who can block or an FB/TE with speed, Accel, pass catch, blocking, break tackle, ball carry and avoid fumble at the FB1 and RB2 slots.
It's also important that your RBs, FB's and TE's can pass block AND run block in 4.6 to help out your QB when trying to pass. The more time and protection he can get the better.