eNotes editors are freelancers who sign on to the eNotes site and write answers to titles on topics on which they are qualified. If you are a premium user, your questions are more likely to be answered than those of free users because editors are paid more to answer premium questions.
As to how quickly specific questions are answered, it really depends on the numbers of editors expert in your area who log on. In general, clearly stated questions which address one specific question, and can be answered relatively simply, are more likely to be answered than vague or unclear questions.
Otherwise, it's really just a matter of when editors in your specific area happen to be working.