Most universities with co-op programs offer a certain degree of flexibility. It depends on the needs of industry and the wishes of students. It is possible to extend the usual four-month placement to eight months. Generally, placements are done in four-month increments to correspond with terms. We have to use four-month increments so that students can work co-op into their program.
Some universities offer co-op placements to students only once over the course of the program, and those placements can last 8 or 12 months. When I was dean of the University of Saskatchewan's College of Engineering, students would do 16-month placements. But they could do so only after completing their third year.