Thank you for taking the time to make this post. Just the fact that you are genuinely concerned about trying to respond to the mountain of email speaks highly of your character, which is far more important than whether or not you can actually accomplish that impossible task. As a high public profile Nikonian, you represent the rest of us very well - not just with technical expterise, but as a quality individual. For the majority of the Nikonian community, no apology is ever needed from you for not responding to an email. And you don't need to thank us for our patience, but we do thank you for yours. You obviously have a lot of diverse responsibilities pulling you in very different directons.
Remember, there's a finite limit on just how much work any of one us can take on before we start to burn out. Keep up the good work, but keep it enjoyable for yourself too. Your Nikonian friends are behind you all the way! We want to help, not add stress.
My only suggestion, although with you being an author you are probably already using it, would be to get some voice recognition software. I just started using Dragon Naturally Speaking about a year ago. It works amazingly well, and is a huge time saver for handling email, and other tasks where typing is involved. I was skeptical at first, but it really does perform as promised.