Use it or lose it...
I'm presently in the process of trying to learn the order of battle...
I was doing really well, I had locked down the 1st Corps in about a week.  Well I took a week off (vacation) and stopped doing the memorization drills that worked so well for me in paramedic school.
I literally lost about 1/3 of what I had known cold.
I did get to go to Gettysburg for 2 days though, so it's a trade off.
After a big step back, I have rebounded, and am now working on learning the 2nd Corps.

I will post pix from my trip tomorrow (or later tonight)