I buy my base grain pre-crushed in 25kg sacks. I don't brew that often so a sack typically lasts me a number of months (I know this might not be ideal for freshness, but this is besides the point...)
Anyway, I am trying to dial in all the aspects of my system so I can get more accurate results...and I think I have started to notice a trend in my efficiency. I hit around 70% on average. This may just be coincidence, but I get the feeling that my efficiency is always lower towards the beginning of the sack, then increases for the last couple of brews. Perhaps over time the sugars are settling at the bottom of the bag and the husks towards the top?
Has anyone else noticed anything like this?