IANAL so be sure to confirm this with a real patent attorney, but...
>... or the idea is forever unpatentable.
As I understand it, this is incorrect. Provisional patents, unless followed up by a non-provisional filing within a year, are never published and never searched and and never considered as prior art, or as anything, going forward. They may as well not exist, since typically nobody even looks at them unless a proper non-provisional is filed. You can very well file a patent, or heck, yet another provisional on the same idea (resulting in a new priority date, of course). The risk you run is somebody else filing on, or simply describing, that invention in the interim, in which case you lose rights to claim as your own in the new first-to-file regime.
Edit: I completely understand your hesitation, as it often takes many years to bring even a small innovation to the market, so the choice is hard. That said, a provisional can cost as little as $65 if you qualify as a microentity and file it yourself. All you need is to file a detailed description, and let a real attorney / agent draft the non-provisional if you decide to convert. But be sure to be excruciatingly detailed about every aspect of your invention, else it can limit what you claim in the non-provisional. My view is, for less than a hundred bucks, it may be worth filing one just in case.