Seems to me you have about the same chance to up your Swordfighting skill from actual combat (not just whetting your blade on militia) as you do from six hours with the Expert trainer. Combat usually lasts one hour. I don't know how you'd learn more in one hour watching a chaotic fight while trying to issue orders and keep your low-paid men from wandering off to play whatever they had in place of Nintendo back then (Knifey Spoony, I'd wager).
As far as RP goes, my main Warrior guy surrounds himself with infantry like ablative armor and fights whoever gets through. When he isn't such a reeking newbie and becomes a Hero, he will be at the front of every charge. The various codes of conduct forbid killing a nobleman in war in favor of capture and ransom (even in history, right up to the Revolutionary War where the Americans got the brilliant idea to shoot the colorful men on horses), but such protections would be tough to apply to a guy at the very front of an infantry wedge, the very first to meet enemy combatants.
