No with promoted listings you do not get charged up front like listing insertion fee's. For the period you chose to run a campaign if a buyer clicks on a add for your item then completes the purchase in 30 days from clicking on the add you will get charged the ad rate you set for that listing. If your current campaign is ending today and you want to continue using promoted listings then tomorrow you will need to set up a new campaign to replace it.
Also with insertion fees and store subscription fees ebay will not prorate or partial refund for periods that they have issues with users accessing their site or using all of its features.
