The clock is always ticking. You have no idea when you find a vulnerability who knows about it or how or whether it is currently being actively exploited. A choice to delay disclosure is a choice to take on the risk that the bug is being actively exploited in order to reduce the gap (and risk in that gap) between public disclosure and remediations being available. But critically, it is a risk that is being forced on the users of the software. They are unable to make an informed decision about accepting the risk because they don't know there is a risk. Public disclosure, sooner rather than later MUST be the goal of all bug reports, no matter how serious and no matter how overworked the maintainers.