When colleges discuss credit requirements for a master's degree, they're listed in terms of options. The primary option is similar across different schools. You must have 24 hours of actual coursework on campus (transfer credits vary depending on the university), and you'll be required to write a thesis that is the equivalent of at least 6 hours of coursework. The research hours for your thesis can be worked out with your academic adviser to make certain that they meet the necessary prerequisites for your degree, as well.
Option II, the primary alternative for master's students, varies across campuses. Generally speaking, though, Option II allows students to forego the independent research and added time required for the thesis and to replace that research with additional coursework to make up the hours. Some universities, such as the the University of Alabama, simply allow master's students to take an additional 6 hours of coursework, evening out to 30 hours. Other colleges, like the University of Nebraska, require students to do more coursework if they forego the independent research; students must accumulate 36, rather than 30, hours of credits.
Students have only a limited time to earn a master's degree. According to the University of North Carolina's "Graduate School Handbook," all graduate students have a maximum of five years to complete their master's degree coursework. That time frame begins at the semester of first registration and expires five years later on that year's commencement date. If a student needs an extension to finish his or her degree, he or she must file a petition with the college board and show ample reason why an extension should be given.