If you want to keep your customers buying from you it is important that they can reach you easily. All too often I see sales people who start climbing the corporate ladder only to lose touch with their customers. They become too difficult to communicate with and ultimately their customers find someone else to buy from.
Accessibility doesn't mean that you have to be on call twenty-four hours a day. It does mean that your customers have to know that you are still looking after them even if you don't actually deal with them on a daily basis. Many customers feel a real sense of connection with their sales people and they can feel betrayed when the sales people are no longer there for them. Once again, it is all a matter of communication, the eternal and constant driving force in the world of sales.
Small business owners in particular seem to struggle with this concept as their business grows. When they start the business they can't seem to do enough for their customers. But then they spend more and more time in the 'back office' doing paperwork, running the business, managing the staff, buying the stock and doing everything but interacting with their customers. Clearly this is a bit confusing for the customers and it is a good way to lose business.
You can determine how accessible you are going to be to your customers by setting boundaries, but beware of the trap of looking inwards at your business and not outwards at your customers. Be as accessible as possible. Communicate with your customers and let them know that you are always going to be there if they need you. Most importantly of all, only send this message if you really mean it.