When layover flights are booked with the same airline, your baggage will be automatically transferred through to your final destination. However, if the two flights are with different airlines, you may have to claim and re-check your baggage during your layover.
What happens to checked bags during long layover?
As a general rule, most airlines will NOT automatically check your luggage through for an overnight connection. You will normally need collect your luggage when you land, and re-check it the following morning. This is normally a good thing as it allows you access to your luggage for your overnight stay.
Can you leave airport during layover with luggage?
During domestic layovers, you are free to leave the airport. If your domestic layover is longer than one hour, you should expect to receive two boarding permits. If you want to check out local points of interest, make sure you get your second boarding pass and print it out before you leave.