One piece of advice I would give customer service-wise (based on my dealings with another outfit) would be to reply to each request with a "number of orders in front of you" amount. If I email John to be placed on the list and he replies "there are 22 orders in front of you" then I know I'm sitting at about the 4 month mark. Or, maybe it's better measured in drawer/shelf units, not "sets" or "orders", as some people will order six drawers while others will order a drawer and two shelves.
"John, I'd like three drawers and a shelf"
"Okay, Clint. There are currently 47 units ahead of you"
At 30 units/mo (5 sets of 6) I then know I should be getting contacted next month.
Maybe?
If I were on John's side taking the orders, I'd probably send out a monthly, or bi-weekly, mass email (bcc) with the list of current orders (or just keep it updated and posted online) so there was always a constant communication of where you stood in the queue.
Just the first thoughts in my mind...