Question : Is there another local airport that can get you to Miami?
Answer : Departing from Santos Dumont Airport is not the only way to get to Miami International Airport. Try searching for flights from Galeao Antonio Carlos Jobim International Airport (GIG) as well. Over the upcoming months, flights from GIG to MIA are being priced 38% cheaper than flights from SDU to MIA. Being only eight miles away, it's easily accessible for most.
Question : How long do most people stay in Miami?
Answer : Of course you're not most people, but if you were, you'd stay roughly 42 days.