I've had no trouble buying ready crushed in bulk so far. I bought 25k of Maris otter and 25k of Dingemans Pilsen last year, the MO I finished fairly recently, I'm still using the Pilsen. Efficiency hasn't dropped over time, and it tastes just the same as when I first started using it. You just have to keep it sealed up, stop moisture from getting at it.
I don't buy my speciality/roast malts in bulk, as I use too wide a variety and would end up with a house full. I'd be tempted to get my Munich in bulk though, but 2 25k sacks is enough to store as it is... It's an option though when the Pilsen runs out, if I decide not to bother with another (I only really use it for Saisons, and you can make them just as easily with Hook Head I reckon). I get through a LOT of Munich as I use it in pretty much everything....
HBC sell in 10k lots though as well, which is a nice compromise. Good way of buying bulk without going full on I reckon.