I haven't noticed loss of experience but I haven't looked for it neither. I'll start keeping an eye out for that. Constant training can help teach you to do something faster and better. Like reloading and shooting. The professional armies could do this quite well compared to say militia or irregulars. The faster you can reload the faster you can kill people. I've heard that soldiers often had a habit of wanting to aim too high so they were often told to 'aim low' to allow for the recoil of the musket and the natural tendency to aim too high.

Discipline will also teach the soldier not to turn and run at the first volley as well. A good example is that American militia had problems in the beginning against seasoned British troops during the Revolutionary War. Takes a lot of nerve to walk up to within 100 yards or less (often less) of someone and and boldly stand there and take a volley while you reload or wait for a command to fire. Nothing like watching a line of men not too far away take aim at you and fire to scare you silly.