A quote from a very interesting old book, 'Anonymous. The London and Country Brewer, 1736.
'...Many are likewise so sagacious as to grind their brown Malt a Fortnight before they use it, and keep it in a dry Place from the influence of too moist an Air, that it may become mellower by losing in a great measure the fury of its harsh fiery Particles, and its steely nature, which this sort of Malt acquires on the Kiln....But the pale Malt will be fit for use at a Week's end, because the leisureness of their drying endows them with a softness...'
And another learned quote by E. Hughes. A Treatise on the Brewing of Beer, 1796.
'...I have known many persons neglect giving orders for their malt till the day before they intend to brew; but malt should be ground four or five days, or a week would not be too long for brown malt, but great care must be taken to keep it in a dry place...'
Old advice but good advice by my reckoning.