An excellent point that ks629 brought up is that historical knowledge of the products at a medical device company is invaluable to the company. If a company has a culture where engineers are hired only for the duration of a project and then are let go, the company is losing a valuable resource for knowledge of the device. Although the medical device industry is intrinsically well documented (and everything about the product and its design history should be recorded somewhere), someone with experience with the product will still be a better resource than someone who is brought in cold on the next project. It is the job of human resources to try and keep these valuable people with the company by providing competitive salaries and benefits so that the employee will not want to find somewhere else to work.