How long should a long-term auction last?

Long-term auctions have no strict deadline. All long-term auctions use the Ascending Clock Algorithm. 

As a result, auctions may extend for multiple rounds if there is overdemand.

For monthly auctions, the last round of the auction takes place on the last working day of the month preceding the start of the runtime, between 13:00 and 14:00 CET.

If no capacity is allocated by the end of this round, the auction is terminated and the unallocated capacity is re-marketed in the next short-term auctions.