"And no, I don't think it unrealistic in the slightest, that charging cavalry moves a long way in a short span of time.  It did in real life, too.The only thing needed is no road movement bonus in a turn you are going to melee - for infantry or cavalry.  That is really about it."  
Yes that was my big problem with BG, the road movement combined with charge, for a 1500 yard charge. 
"Cutting the range of charging cavalry to 600 yards on the other hand, is silly.  That is 1.4 mph, half a walking pace of a man on foot.  1400 yards in 15 minutes, which is what you get with 15 MPs for cavalry and double moves for a charge allowed, is all of 3.2 mph.  In other words, a walk.  Naturally it represents 2-3 times that speed trotting or cantering in "your half" of the turn - but it is still a very low figure for charging cavalry.  Halving it is not realism; more like neutering."
In 
Wellington's Victory I recall those charge zones were 600 yards. That's about how far a normal horse can run full out before getting winded. The longest sprint for thoroughbred horses is 6 furlongs or about 1300 yards but that's with a really light weight jock, on a leveled track and they do it once a day. Cavalry horses are carrying a fully armed man, charging on an uneven field, being shot at after standing around a battlefield all day, not being pampered in a paddock. People move slower on a battlefield and so do horses methinks. Thanks for your analysis. You should have come into this discussion earlier Jason. jonny 
