Save the date

A quick thought for push-based marketing. If you are trying to market for a specific event, do you:

• Keep the date of the event in front of your customer from the beginning, possibly losing immediate interest (because they feel like there is time to shop around or just not enough urgency yet), but providing a useful reminder that the event is coming up?
  
• Mention the event, but don't tell the customer a specific date (to create a sense of urgency -- "oh no, I should buy something now for Father's Day!")?
• A combination of the two (assuming you have multiple opportunities), for example not mentioning the date until it is imminent (again, all about urgency), mentioning the date initially but not after the first e-mail or flyer?

Not being in E-commerce, my opportunities to test this are limited, but it seems like something that could be a significant factor. Now is the time the ridiculous Amazon customer base would come in handy. Test away!