The USPTO gives you one year to convert your provisional patent to a formal patent. If you do not convert your provisional patent to a formal patent, your provisional patent protection simply expires. If you are still not ready to file for a formal patent after the one-year period, you can renew your provisional patent protection by simply refilling for a provisional patent – if and only if you haven’t publically disclosed the subject matter of your provisional more than 12 months prior to the re-filing date. However, you will only be allowed to claim priority to the date of filing for the non-expired provisional patent.
If you are interested in more detail related to your situation it is best to speak with an attorney.
Yuri Eliezer heads the intellectual property practice group at Founders Legal. As an entrepreneur who saw the importance of early-stage patent protection, Yuri founded SmartUp®. Clients he has served include Microsoft, Cisco, Cox, AT&T, General Electric, the Georgia Institute of Technology, and Coca-Cola.