Auto-reminders for an event are controlled by the host of the event! If you'd like to receive fewer auto-reminders, you can ask the host to change the settings on their event.
If you've RSVP'd "Going," the default settings are to send reminders the day before the event and 2 hours before the event. If you've RSVP'd "Maybe," the default settings are reminders 2 weeks before, 1 week before, and 1 day before the event.