Blessed Dask releases

For the past year plus we've been releasing Dask on a more-or-less regular two-week cadence. Recently we've been experimenting with weekly releases (xref https://github.com/dask/community/issues/84). In the last monthly meeting, the idea of having a "blessed" version of Dask, which is released less often than the usual one or two-week cadence releases, was raised by folks from RAPIDS and Capital One as something that could be valuable to the Dask ecosystem of libraries.

I'm opening this issue to keep that discussion going and pin down how we want to go about this. A couple of logistical questions come to mind:

1. How often do we want to release a blessed version? Once a month? Once a quarter?
2. How should we indicate a version is blessed? For example, we could have a page in the docs with a table indicating which releases are blessed. We could also give blessed releases a special version number (xref https://github.com/dask/community/issues/100)

cc @datametrician @kkraus14 @mmccarty for any additional thoughts or context