No fixed timetable. For example, when will Vision Pro- released Feb 2, 2024- appear in the refurb store? Going by threads here, there & everywhere, Apple should have almost all of them back and needing to be moved. And yet, not a one yet, just shy of a YEAR after release.
Refurb pricing discount is usually 10%-15% at best... so no, not necessarily better pricing than even weekly "sales" through third parties. The one advantage of refurb over sales is that- if you keep checking often enough- you can get the variety of configs in refurb offers while third party stores are generally base specs or barely more than base specs. If you want a high-spec M4 MBpro, refurb could be the best way to get a sale price you won't find in new MBpro sales at third parties.