I was arrested for possession of a controlled substance found in my truck over two years ago and I have never been charged. Nor has it has not gone before the grand jury. Is there some kind of time limit or can they drag it out for as long as they want?

There is a time limit for charging a person with almost every crime, including drug crimes. Murder is the principal exception, with some types of sexual assault crimes being others. The time limits vary from state to state and federally. It is called the "statute of limitations" which means the time period within which the state must file charges against you after learning of possible criminal behavior. In your case, this would be the date of your arrest. The principal reason for a statute of limitations is fairness. The burden of proof in establishing a crime rests with the government. A person charged with a crime has a right to present a defense. But as time passes, memories fade, witnesses relocate, die or otherwise become unavailable, and evidence may be lost. This can hamper an accused's ability to prepare and present a defense. Also, public policy favors closure at some point on crimes. In Texas, where you are from, the time period for filing charges in a felony drug case is three years. For a misdemeanor drug offense, it is two years. For a federal offense, the time period to bring felony drug charges is five years.