Increases vary by a number of factors including overall payment history, age of the CA, added lates by the CA, reporting status, and number of CAs remaining. In general, you may see anywhere from 20-80 points. My second to last CA fell off in Febraury due to the 7 yrs and received around 24 points. I have one CA left ( 4 yo AFNI) and expect about a 50-60 point bump with its removal.
COs are different. You could remove a CO with a balance due and actually loose points. History plays into COs in a big way.