jjw509 wrote: The game wants to keep replacement chits at 10% so when you have the big free armies come in it chokes your resources for building. I would rather build armies first then replacements closer to when they are needed. Maybe in 1862 I might switch it back on since it is more likely battles will be occurring and a buffer of chits for replacements will be needed.
That's hitting the nail on the head. It's important to note that you don't actually get any free replacements from auto, it just automates buying them for you. Since you have to check that screen every turn anyway it doesn't help at all to automate them and often interferes with your other priorities. Once the fighting gets hot and heavy you WILL have turns where you spend everything on replacements, especially as the Confederates.
Replacements are available immediately, so once you hit the turn button your troops can start drawing from any replacements you just purchased. So, if you have zero replacements of a particular type and purchase some, you will not have to wait another turn before they start working. It is usually only necessary to keep a small buffer of replacements on hand, unless you expect the fighting to be so intense that you will use more replacements than you can afford to buy with a single turn's resources, which does sometimes happen but is the exception not the rule.
As the Union you need even less of a buffer, since you draw replacements so slowly that you are rarely able to actually use all the chits you have on hand in a single turn. You still need the same amount of chits in the end, but since you won't be able to use them all at once you can spread the purchases out over a couple of turns.
As the CSA I only rarely buy heavy artillery chits, since they are really expensive and get burned up filling out Coastal Artillery in all your forts.