Tip #6 - Don't put all your eggs in one basket

Whether it is a distributor or a large retailer, be wary of letting any single relationship represent too much of your business.  There are countless horror stories of businesses that failed when they lost a single account that represented the majority of their profits.

Ryan Montague from Gourmet Business Solutions, a forward thinking consultancy with fresh ideas on the specialty food industry, wrote the below article that includes Costco's position on being a supplier's biggest customer.  

He makes the situation very clear in his post:

For example, I learned that Costco typically doesn’t like to sell to a business whose sales with Costco represent more than 20% of their overall business. The reason: Costco doesn’t want to be the “bad guy” if they drop a Costco-dependant line that could sink without their business from Costco. Just goes to show that all the corporate giants aren’t so cut-throat after-all (which is common when dealing with the larger food retailers and distributors).

http://blog.gourmetbusinesssolutions.com/2009/01/02/selling-food-to-club-stores-costco-sams-club-bjs/