Legal language is very different from the language we all use in our daily lives. Because of this, your question is a bit confusing. When you say you "got a DUII" I assume you were arrested and charged with D.U.I.I. When you say "they did not file a case against you"...what does that mean? Who is "they"? Sometimes if a D.A. decides not to file an official charge against you (for many different reasons) they will do what is known as a "no complaint". A clerk will typically read a list of names before the judge appears and tell those people that they may leave and no "complaint" has been filed. That rarely happens with DUIIs but it is possible.
If you are "no complainted", there is no statute of limitaions. A D.A. may file a complaint against you at any time. That also rarely happens unless new evidence surfaces.
Hope this answers your question.
Best of luck.