I just wanted to highlight selling products like this (consumables) as being a good option to consider on site such as eBay. Selling consumable products is a great way to build a solid customer base over time.
I would suggest you need to build up a strong product profile, but when you have something like that in place, provide a great service, then you are giving yourself every chance of repeat business every time a customer needs to repurchase!
Building up a loyal customer base is an important element for any business wanting to be successful in the long term. The higher the level of repeat business you can do, the less new business you need to find, and if you are providing a good service to your customers, repeat business is always far easier to develop than developing new business constantly.
Most long term successful business's will have a good ratio of repeat customers and new business, the higher the repeat business ratio will usually equate into the business's ongoing growth.