What is the best time to patent our product?

In March, 2013, the US patent system went to a first-to-file system in alignment with much, if not all, of the rest of the world. Therefore the first one to file a patent application with respect to a particular invention - system, method, machine, product, whatever - is automatically the senior party and will have senior rights offensively if they receive a patent, and defensively even if they do not receive a patent, their application will be published and will serve as prior art against those who file later applications for essentially the same invention. Accordingly, it is in your best interest to file a patent application as soon as possible in order to protect your future rights. If you are still in the development stage, you would be wise to file a provisional patent application for what you have already developed. You must then file a non-provisional patent application or a PCT application within one year from the filing date of your provisional patent application but your provisional patent application will effectively provide you with a priority date relative to others who may file later applications for similar subject matter provided that your provisional application does in fact provide an enabling disclosure of your invention. In other words, the provisional application, just as with a non-provisional or PCT application, must be complete, accurate, and thorough. If you in fact develop your invention further, or develop additional embodiments, you can then file one or more provisional applications within the one year time frame and then file your non-provisional or PCT application within one year from the earliest provisional patent application. A good technique in dealing with subsequent provisional applications is to effectively add the new developments or embodiments to your original provisional application and then use your last omnibus provisional application as your non-provisional or PCT application - in this manner, nothing gets inadvertently omitted from your non-provisional or PCT application.