Blue farm, you should supply a little more information, as it might change how people see your questions.

From a silage perspective, I think in terms of the dairy farmer.  However, if you are a beef farmer, the answers might be different.  And if you are growing corn to sell - as either silage or grain - again, your answers might be different.

The dairy farmer is always going to meet corn silage needs before he thinks about harvesting corn for grain.  Corn silage is less expensive to grow yourself, than it is to buy; and transporting corn silage any distance can get quite expensive.  So, dairy farmers will meet corn silage needs, and buy shelled corn if they can't grow enough grain for their needs. Some nutritionists do not like to feed "green" - uncured - corn silage; so, some farmers will have enough corn silage on hand for, say, 14,15, even 16 months.  It helps to prevent loss of milk production when switching from last year's corn silage to new crop corn silage.