When you’re ready to work and can’t. Take good care of yourself!!

What I read is that you should either varnish your painting as soon as it is dry enough to do so, or you should wait a year (!) to make sure that it is completely dry. The reason for this is that when the painting is just dry enough, the varnish will actually bond with the paint and you will never have to worry about cracking, otherwise if you varnish after a few months, parts of the painting may not be entirely dry and there could be cracking. If you wait until the painting is completely dry then it acts as a new layer on the surface of the paiting and does not bond with the paint, but it will not then seal in any moisture that could lead to cracking.

That’s what I recently read.