Roasted coffee beans last weeks to a few months, but it depends.
According to SCAA, the factors that affect the freshness of coffee the most are:
The state of coffee (whole beans vs ground), environmental influences (oxygen, temperature, and moisture), and time.
The longer you keep the coffee, the more these conditions will influence the coffee flavor and aroma. Fortunately, there are ways to keep your coffee fresh for longer.

Parameters That Impact Coffee Freshness and Shelf Life

Whole Bean vs Ground

Whole beans have a longer shelf life than ground coffee. Whole beans remain fresh from weeks to several months while ground coffee begins to degrade almost immediately and remains fresh for about two weeks to a month. This is because the oil and aroma are trapped within the coffee bean and once it is ground, the aroma is released and quickly gets lost in the environment. Also, ground coffee has a smaller surface area, which accelerates degassing and staying.

Oxygen

Oxygen has the strongest impact on flavor and aroma. When certain coffee molecules that are responsible for the rich coffee aromas and flavors encounter oxygen, they degrade and produce the rancid taste. This reaction is called oxidation and it is a critical reason for your coffee to become stale and taste rancid.

Temperature

Ideally, you would want to store the coffee in a cool place 15°C (59°F) to minimize the impact of temperature on the coffee. Room temperature 18° – 25°C (64.4° – 77°F) will work fine though. The only thing to avoid is a warm temperature. Anything 30°C (86°F) and above will accelerate all the chemical reactions that negatively influence the coffee flavor.

Moisture

An excess in moisture will shorten the shelf life of the coffee and will help create rancidity. It is recommended to avoid a high moisture environment given that roasted coffee can still absorb water, and water activity will accelerate coffee staling.

How to Store Coffee?

Store your coffee in an airtight container.
Keep your coffee in a cool and preferably dark location.
Avoid a high moisture environment.

Conclusion

Time is coffee’s biggest enemy. Coffee will start degrading as soon as it leaves the roaster. To have that fresh coffee taste get whole beans rather than ground and store the coffee appropriately. Always buy freshly roasted coffee, enough to last you a couple of weeks to a month, to enjoy all the wonderful flavors your coffee has to offer. If you are feeling adventurous, you can get a home roaster and try roasting your own green coffee beans, nothing will beat that fresh taste!