Delta SkyMiles are typically valued at around 1.1 cents per mile, but this can vary based on how you use them. You earn SkyMiles when you buy Delta flights, use a Delta co-branded credit card or make purchases with select partners through SkyMiles Shopping. Famously, Delta SkyMiles don't expire. As long as you log into your account occasionally, you can accumulate to your heart's content.
Like many other airlines, Delta uses dynamic pricing for points, so there's no award chart you can easily game for extra value. The benefit is that there are no blackout dates. If you want to stretch your points, look for flights during low-demand periods or when cash fares are discounted, such as mid-week or outside peak travel seasons.
If you're trying to get an above-average redemption, Delta upgrades or long-haul international flights can push the value closer to 2 cents per mile. The Delta SkyMiles® Gold American Express Card and other high annual fee cards also offer TakeOff 15, a 15% discount on all Delta-operated award flight redemptions. If you fly enough with Delta, this is a worthwhile option to make the card's benefits worth the annual fee.