Just wondering how the best way to charge clients in regard to keeping their wordpress website up to data and secure with the latest wordpress patches and plugins, as well as troubleshooting problems. 

Do people here charge out the work at an hourly rate? Or do they charge a set amount per month and hope that that covers the time.

Also how frequently do people update things like plugins, as well as mange those updates?. Normally I do them as soon as their are released. I do realise that most plugins can be easily updated inside wordpress, but with wordpress updates, the site and database first needs backing up, and there can sometimes be theme compatibility problems that then need the theme updating or CSS changes. I see there are some automated updating system, but the one I tried WP remote wasn't much good.