Four years in a term, Two terms max. The longest that a president can hold office is ten years. Notably, there are exceptions that limit it, such as impeachment or death.
After the president is removed from office, the vice president is put into office to serve the rest of the term, and after that, he may run for reelection (Though, unless he spent less than two years as VP, he can only go one other term.) If the VP is removed, then it goes to the Treasurer, and on and on.