To put the contents of your application into the prior art for other’s future applications as early as possible, you could publish or publicly disclose the contents the day after you file.
That isn’t wise because there may be some reason your application doesn’t get the priority date you expected. The other limit is 18 months after the earliest claimed priority date since it will be published by the IB at that point.
A reason to hold off disclosure is If the applicant decides to keep the invention as a trade secret and informs the IB soon enough, the application can be withdrawn and publication avoided.
If your thought is to get an idea of patentability and then decide whether to proceed to a possible grant or, alternatively, stop publication and keep it as a trade secret then disclosure after a favorable ISR would be a way to establish your content as an early prior art to other’s applications with reasonable expectations of a granted patent.