Dark chocolate likes to be stored within the temperature range of 12-22° C (53-72° F). Temperatures as high as 25° C (77° F) are usually fine. The official melting point of dark chocolate is around 30° C (86° F).
Officially, the shelf life of dark chocolate is two years. Unofficially, it should last much longer than that - there are documented reports of dark chocolate still being edible after 100 years of storage. As part of our own experiment, we have chocolate bars that have been stored in our office for up to six years, and they are still in excellent condition. But we don’t recommend trying that at home. Why wait?