how quickly do you answer support emails?
modoc: Use a ticketing system or issue tracker that creates tickets based off of e-mail (I like Jira personally).  Setup an auto-reply to let them know their e-mail was received, and someone is looking into it.  If your ticketing system is world facing (which I think is a nice idea), ask them to visit their ticket (Jira can auto-create accounts for people who don't have them yet when they send an e-mail that creates a ticket), and set the priority.Give your timezone/part-time issues, I'd provide a cell phone or something for people to use in case of dire emergency.  If people abuse it, you cut off their support service.I'd also instrument as much as possible so that in the event of a disaster you are first to know, not last.  I use a heavily customized nagios setup that sends SMSes to my cell phone.  Works out well.