Not once you've signed the contract for 4 years. I signed the contract at the time of application. They may question why you don't want the additional scholarship time, which could affect your competitiveness. If you had a reason -already have a diff. commitment, etc, I would find a way to explain. If you just don't want to spend the additional time, I wouldn't bother applying, and go LRP. NHSC tracks scholar retention after obligation fulfillment, it's one of their metrics. They don't want people who stay 2-3 years and leave, which is clear if you read criteria.