The boost on starts from the day of payment and lasts till the event date or next 30 days, whichever is earlier.
Social media ad duration depends on the plan that you have purchased. Usually, with an ad credit of USD 10, your ad would run for about 5 days. You can always purchase additional Ad Credits to keep your Social Media ads running.
Email credits are issued within 1 business day of the payment and can be used as you please.