Da seção do SRD sobre Magias Arcanas :
Rest
To prepare her daily spells, a wizard must first sleep for 8 hours. The wizard does not have to slumber for every minute of the time, but she must refrain from movement, combat, spellcasting, skill use, conversation, or any other fairly demanding physical or mental task during the rest period. If her rest is interrupted, each interruption adds 1 hour to the total amount of time she has to rest in order to clear her mind, and she must have at least 1 hour of uninterrupted rest immediately prior to preparing her spells. If the character does not need to sleep for some reason, she still must have 8 hours of restful calm before preparing any spells.
(ênfase minha)
O SRD não menciona a capacidade dos elfos de dormir quatro horas de sono, mas, como eu me lembro, essa habilidade não reduziu a necessidade de um elfo de descansar; só permitia que eles estivessem conscientes durante parte do tempo.
Eu diria que se aplica aqui: o elfo ainda precisa de oito horas de "tranquilidade tranquila" antes de preparar feitiços diários, mas pode ser consciente durante parte desse tempo.
Magias Divinas são muito mais simples:
Time of Day
A divine spellcaster chooses and prepares spells ahead of time, just as a wizard does. However, a divine spellcaster does not require a period of rest to prepare spells. Instead, the character chooses a particular part of the day to pray and receive spells. The time is usually associated with some daily event. If some event prevents a character from praying at the proper time, he must do so as soon as possible. If the character does not stop to pray for spells at the first opportunity, he must wait until the next day to prepare spells.
Após o período de descanso / na hora específica do dia, é necessária uma hora para preparar os feitiços. Há algumas nuances a mais (os assistentes podem deixar espaços vazios, por exemplo), mas o SRD faz um bom trabalho ao cobrir as regras claramente.