I still can’t find anything definitive on timeframe but the last...

I still can’t find anything definitive on timeframe but the last paragraph could translate to a short space of time before moving straight into the pivotal trial. 30 days would be a bonus.

Some IDE studies are categorized as an EFS. These studies allow for early clinical evaluation of devices to provide proof of principle and initial clinical safety data. These studies generally include a small number of study subjects (15 or fewer), can involve the use of a device design that may be early in development (i.e., a nonfinalized design), and/or are initiated when clinical experience is necessary due to a lack of available or appropriate non- clinical testing methods to advance the device development process. They can be conducted for new, unapproved devices or for a new intended use for a device already approved or cleared for another indication. EFSs are intended to obtain initial insights into basic device safety and proof of concept. FDA approval of an EFS IDE allows US patients early access to potentially beneficial medical devices and enables such a therapy to be studied in the US first in the world.
For some device development programs, an EFS may be followed by a traditional feasibility study, which is usually intended to evaluate a finalized or near-finalized device design and is generally supported by more non- clinical or prior clinical data. Traditional feasibility studies enroll more subjects than an EFS and typically collect additional safety and effectiveness data to appropriately inform a larger expanded study (i.e., a pivotal study).
EFS IDE Best Practices to Initiate a Clinical Trial
The EFS guidance document provides a variety of best practices to facilitate EFS approval that may involve novel technologies, patient populations with serious conditions who lack treatment options, and complex trial designs, with sometimes less nonclinical testing than typically observed for initiating a feasibility or pivotal study.

Once sufficient clinical safety and effectiveness data have been collected from an EFS sponsors often transition to a pivotal study, which provides key clinical safety and effectiveness data to support a marketing application.