Meal worms are commonly used as a standard feeder for most insectivorous pets. With general ease of production meal worms are usually the least expensive feeder insect option.
Meal worms are fairly nutritionally complete but still require adjustment. One way to help improve this is to feed the insects high quality foods prior to feeding the insects to your pet. This process is called gut loading, which should be done 24 to 48 hours prior to feeding to your reptile. This requires some planning, but is well worth it. Please note that gut loaded insects should still be dusted with calcium and vitamins as per your veterinarian's recommendations.
Meal worms can live a variable amount of time especially when kept cold. Keeping meal worms in the refrigerator will make them last indefinitely. Keeping meal worms at room temperature will provide you with 4-6 weeks approximately before having some pupate and turn to beetles. Once a week or so you should remove the meal worms from the fridge for 24 hours to allow them time to shed and eat.