I have had Cingular for about 5 years now. They update automaticly and have for several years.
I did have some issues a year or so ago with the SIM cards on two phones. I had to go in to a Cingular store and get new SIM's put in them. I had those particular phones for about two years and never turned them off
The SIM's got overloaded or something. Cingular reccommended that once a week I turn them off for a few minutes, then turn them back on. I understand this clears the SIM's of old stuff and ensures they update.