Will I have to do another manual update when last year's date rolls around this year?"
Since it doesn't look like this was answered correctly, are you asking will you have to adjust the time again, when the "normal" time change date arrives?
The answer to that is no, the 3300 will *never* change time on it's own. It always needs to be done by an outside source, either a human from the Group Admin tool, or via Ops/Entman.