Normally I brew Spring and Fall. I brew maybe 7-8 x 5 gallon batches a year, so my grain needs aren't nearly that of people who are brewing 10 or more gallons at a time, and making who knows how much...well, let's not go there.
I usually make an order for a brewing season consisting of a bag of 2-row, and then the other grains I need and relevant supplies. If I forget something common, there's a wall in a big beverage mart locally that has beer & wine making supplies, so I can grab it there. This way I can make only a few online orders per year and minimize costs.