When you purchase a subscription, it comes with a specific set of credits.
When are credits dispensed?
As long as you have an active subscription, monthly subscriptions will give you the allotted credits each month and annual subscriptions will dispense the credits each year.
Do credits expire?
Credits NEVER expire as long as your subscription is active.
How are credits charged?
Credits are charged from your account each time you get back a result. If you click to search for a profile and no data returns, no credit is charge.
What happens if I run out of credits?
No worries. If you just need a boost, go ahead and purchase a new subscription. It will immediately add more credits to your account and "reset" your billing cycle to the day you purchase it so there are no double charges. You can only have one active subscription at any point.