I need some help understanding how to support clients. I sell website driven on open-source CMS's, so naturally I train the clients on how to edit their site. Prior to publishing the sites are checked against all browsers etc. Recently however, I've had a fairly unreasonable client, one which demands constant attention and constant work.

I always support my websites and iron out problems even after website launch. 30-days is sufficient for this.

After checking other web design companies many sell their support separately, or provide it with hosting. Some companies provide hours-rate support, depending on the company.

How do you guy around supporting clients? What would you do if you had a client who demanded constant attention, and viewed it as part of the deal? How would you come around this? When is enough enough? Would charging an hourly rate solve this problem, or would you offer a package deal? Even if you offered a package support deal, what would you need to do to overcome unreasonable clients?

Ideally this thread is not to solve my issue, but to talk about your general experiences, and what you did to overcome them so that we could learn from each other.