Exposure to air: Preground coffee is exposed to more air, as it has a larger surface area than whole beans. Oxygen can interact with the coffee, leading to the deterioration of flavours and aromas. This is the main reason whole bean coffee lasts so much longer than preground.

Time: Coffee starts to lose its freshness shortly after it's roasted. Whole bean coffee will typically stay fresher longer than preground coffee because it takes time for the compounds to degrade.

Storage: Proper storage is crucial for preserving coffee freshness. Both whole bean and preground coffee should be stored in airtight containers in a cool, dark place to extend their shelf life. However, whole beans generally have a advantage due to their lower surface area exposure.

Grinding: For the freshest cup of coffee, it's best to grind your beans just before brewing. This helps preserve the flavors and aromas, which are lost more quickly in preground coffee.

In summary, whole bean coffee has a longer shelf life compared to preground coffee because it has less surface area exposed to air. However, regardless of whether you choose whole bean or preground coffee, it's essential to store it properly and use it within a reasonable timeframe to enjoy the best flavour and aroma.