I am of the opinion that either the number of horses/wargs you get per turn should be decreased or their cost for trained units should be increased. Currently, if you build even a single stables, you will have so many horses that by turn 100 you won't even care anymore about your horse number (and you can trade them to AI without a source of horses for absurd amounts of money). No other resource is like this - crystal is in dire supply almost all the time, and is exceedingly hard to get in decent quantities, and metal is only about half the problem (as it is much easier to use up).
Right now, every single game ends up with a surfeit of wargs or horses in your inventory and they're so plentiful that a single source can supply your entire army forever. If it's not like that for crystal or even metal, this seems unbalanced.
I dislike the fact that this means that once you get a source of horses, there is no reason to build foot soldiers ever again for any reason, because putting your units on horses has absolutely no downside, material or otherwise.