Yesterday a commenter asked how anyone can reply to all community member e-mails in an hour or less. It takes her nearly all day to get through them all.
The answer is fairly simple.
You don't get all the e-mails done in an hour.
You only give yourself an hour to go through it (the hour is arbitrary).
You get through as many as possible in that hour. The rest of the time you spend developing your community.
The danger here is spending more time on unhappy members and ignoring the happy people in your community.
Would you rather spend 20 minutes resolving a minor issue of one member or working on a piece of content that the entire community will like? How about spending those 20 minutes reaching out to potential volunteers who can help answer questions?
Or if you want to simplify this, let resolving individual members problems be the last thing you do in the day. Once you've got all the development activities done, work on the individual responses.