As a brushmaker, I say a brush should not only have time to dry, but also needs a rest between shaves, so a two-week time off is perfect for any brush. Just get a few that will be in service in these off periods.......I assumed this was accepted advice from brush manufacturers in order to extend brush life, and entirely coincidentally of course, to sell more brushes. I agree though that in years gone by brushes were often simply left wet in the mug with the left over soap. I have read threads where members have done this for several months 'just like grandpa used to' and they seem to have suffered no ill effects. As long as mould or fungus does not develop in the knot then I suspect the brush would last for years.
Yes, it was a joke....