My fiancé had violated his probation (Baltimore City) by getting charged with 3 misdemeanors in Washington DC. He is serving time in DC (18 Months) and after that will have to go to MD to see the judge for the violation. His PO says that he will recommend that the judge leave him on supervision and not impose time. I know that ultimately it is up to the judge. He has a 10 year suspended sentence in MD and Im rather nervous about it. Most people tell me that while they can impost the whole 10 years that more than likely the judge won't give the full sentence. Can anyone tell me if judges typically take the advice of the POs and also how often do they impose the whole sentence (when it is a very long one)?

Yes, it is the decision of the Judge. I've seen Judges agree with PO's and I've seen Judges disagree with PO's. There is no set "rule."

I don't think there's a "typical" situation.

A lot of this will depend on what the crimes were.