The short answer is, not too often. Ask your lawyer about the judge's reputation for this. You do have your interview with Probation, and this is very important. Information the PO collects and puts in the sentencing report can definitely influence the judge to depart from the plea agreement.
Assuming you don't have any other issues, you should be fine. Be on time for the Probation appointment, be honest, and pleasant, Your lawyer really should prepare you for the interview- I always do that for my clients.
Best of luck
I must disagree with all my colleagues. If you entered into a plea agreement the judge is bound by it even if probation wants more. When I say bound I mean that if he departs from the plea agreement you have a right to withdraw your plea and start over again. Don't let anyone tell you differently.