I am working in small development firm, our main products are ASP.NET and SQL server based. We are deploying a new version of our product and client wants 4-hour response time technical support. Some of this support time will fall outside regular business hours and our boss asked us how much should we charge for being available outside regular business hours? Is it 50% of our hourly fee, 20% ? Any suggestion is appreciated, he is pushing us to speak up and I don't have any idea. I don't want to underprice my free time. Thanks.