Fwiw, my DS did not study for the placement tests. For reference, he took AP Calc and got a 5 on Calc BC + AB his Senior year. The first placement test was at home in the Spring and didn't seem hard. The second one was during BCT so there was no opportunity to study, he hadn't seen calc in a few months and he was at BCT. He did well enough and was offered Calc III.
My guidance to him was to not to study. Its a placement test - you want an accurate assessment of your abilities as much as USAFA. It doesn't change anything about your status as an appointee - it just helps guide them in placement. I don't know what level of math you hope to get placed into, but you want it to be the "right" one for you. Btw, if they offer you to validate a class, you can choose not to if you want.