Your team has developed an innovative solution or significantly improved your product with a novel process. The approach has been tested and will be implemented in the next product release. Everyone agrees that the solution has never been used before and, as a significant differentiator, ought to be protected by a patent.
So you quickly document the solution and file a provisional application. This is cheap (~$500) and does not even require a lawyer! You breathe a sigh of relief. Your solution has been protected and you can forget about the patenting process for a year.
A year later, you ask you patent lawyer to draft a conventional application from the few pages you originally filed with the patent office. It turns out that 15 more pages must be added to properly describe the invention in order to write enabling claims! Worse still, you learn that only claims in which EACH element was FULLY disclosed by the provisional application will bear the date of the filing of the provisional application. The other claims requiring the additional disclosure will be dated with the filing of the conventional application. Sadly, you may have lost a year of protection by neglecting to disclose some minor details that, although not at the center of the invention, are necessary for it to be enabling!
If you really think your invention is worth patenting, I recommend that you do it right and dedicate resources up front to work with a lawyer to file a complete specification and claims. It is only through the process of writing the claims that you can ensure your description is complete. You may still want to file a provisional application initially (to allow for completion of testing), but at least you will know that you have secured the earliest filing date possible. Better safe than sorry!