I notice that in game terms, you start with an Axis army in the 30's for experience (except the panzers, which are in the 40's). By the mid game, you have maxed out your training level at 40. All you units, including the Axis minors will end up at 40. Some of my attack units, like the panzer divisions would be higher. Playing cards can make a couple of them even higher, although I rarely did that.
As well, the number of replacement points you get is very, very small. Which means that those numbers don't drop very much. And if they happen to drop below 40, in few turns they will climb back up again.
“My logisticians are a humorless lot … they know if my campaign fails, they are the first ones I will slay.” – Alexander the Great