A tip for as many "Save Games" as you want!
Before starting ArmA open your ArmA saved missions folder, in Windows7 it'll look like this: C:\Users\Jim\Documents\ArmA 2\Saved\Campaigns\seals3option3cmp
I have created an extra folder in there called "old saves"
Open Arma and play away, When you want to save at a crucial moment, Alt tab to your open folder, move the save.ArmA2Save file into the "old saves" folder, and then go back to ArmA
You will now have save option available. Do this as often as you want.
If you want to go back to a previous save, just move it from the "old saves" folder back to the correct place and it will be available from your revert menu.
Hope this helps someone,
Cheers, Jim