Wearout Determination

I have this solved through some helper columns, but I was curious if anyone can deduce a single formula solution...

Basically, I have a piece of equipment that can make 4000 units before it breaks. I have a yearly forecast of units needed. I would like to determine at what time the equipment will break (assuming each annual build is evenly distributed by day).

Attached is a sample file with the answers 'hard coded'. It shows that the equipment should break on 8/7/2014.

Thanks,
Pauley