Can I reset an order number counter on a regular basis?
Yes, to choose the option which suits you best, please navigate to System > Configuration > Order Number > Order > Reset Counter on Date Change:
This setting is also available for Invoice, Shipping and RMA* numbers.
*RMA order numbers options are available for Magento EE users only. If you are using Magento CE, you can consider this RMA extension.
See more details on Custom Order Number page