I often find a good way to combat this is to build some of the support costs into your pricing structure. If you factor less billable hours, but increase your hourly rate, it all works out in the end. As long as your customers aren't taking advantage of your time (as many have plenty to do anyway), they'll be thankful that you're going the extra mile to help them out, when they're paying for the support anyway. If you include the price in your quote, and explain your dedication to helping them out with whatever they need, they'll be more than happy with your service and you don't need to lose money. Typically, if a customer is using a LOT of your time, they'll be fine with a consulting fee, especially if they don't do that much business with you in comparison to the amount of time you spend helping them out.