In case you order package with credits that have expiry date set (no matter what number of days is that) once when you set drip feed option to 30 days for example, your link processing will be continued just as requested with your drip feed option set.
For example:
If you have package that have 30 credits expiring in 2 days, you can submit 30 URLs for crawling and set drip feed option to 30. Your submission will be processed with drip feed option set to 30 days and crawled accordingly just as set.