Your remaining search credits, along with the time they are valid for are shown in the top bar of the site at all times:
Search credits do not carry over month to month, it is a monthly allowance based on which account you have:
Free accounts: 3 searches per month
Basic accounts: 100 searches per month
Lite accounts: 300 searches per month
Pro accounts: 1,000 searches per month
Why do search credits not carry over?
When a customer pays for a month of search credits, our systems automatically scale to mean we can meet the demand, which incurs extra costs.
If credits did not expire and carried over, we would be in the position whereby we are paying for large amounts for unused infrastructure. This would mean either we could not run AlsoAsked, or prices would need to increase to cover unused infrastructure.
Based on the feedback we received during our 1-year alpha/beta period, we opted for lower monthly charges along with a refreshed monthly allowance of search credits.
Don't forget, you can stop and start your account monthly, as and when you need it!