Long-term use of naproxen can increase the risk of serious side effects, particularly gastrointestinal bleeding and ulcers. Additionally, prolonged use may lead to renal impairment due to its effect on renal prostaglandins. Cardiovascular risks, such as heart attack or stroke, may also be elevated with long-term NSAID use. It is essential to weigh the benefits and risks when considering naproxen for chronic conditions.