Conversation so far:
What is most notable aspect of Avenged Sevenfold's affinity for concept albums?
Johnny Christ stated in an Ultimate Guitar interview about the writing process of Nightmare: We wanted to have a dark concept record, sort of like The Wall or Operation: Mindcrime“
What inspired Avenged Sevenfold's dark concept record?
On December 28, 2009, Avenged Sevenfold's drummer James The Rev Sullivan was found dead at his home at the age of 28.
what was interesting during the Death of The Rev and Nightmare period for Avenged Sevenfold?
On June 9, 2010, the cause of The Rev's death was revealed to have been an acute polydrug intoxication due to combined effects of Oxycodone, Oxymorphone, Diazepam/Nordiazepam and ethanol“
Was there any discord during the Death of The Rev or disagreement amongst Avenged Sevenfold members?
Avenged Sevenfold members admitted in a number of interviews that they considered disbanding at this point in time.

Question: how long did this album take to make?
Self-contained rewrite: how long did Avenged Sevenfold's nightmare album take to make?