In a relatively short time period I will finally embark on all-grain brewing. I would rather purchase grains online as it is cheaper than the LHBS, but the LHBS won't let me use their crushing equipment unless I bought the grains from them.
I was hoping that there was some hard and fast rules regarding this, like "after 3 days, crushed grains start to lose potency; after 10 days, throw them out."
Does this time frame depend on the type of grain, or are they all about the same?
Is there any (relatively) non-anecdotal evidence in this regard? I.e. did anyone ever purchase 10 pounds of one grain, crush 5 pounds, and brewed n many days later? (Double blind taste tests preferred)