Added 3 minutes later
There aren't 20, but all 6 monks can be converted per week. Training a horse from a monk costs 1300, I think, with an experienced commander and masterful counterattack, and with a perfect one - 750...
And if you recruit an extra 20-30 paladins (in addition to the ones you raise), they will be more useful in battle than all your dryads, even with their super spell - summoning an ash swarm, which everyone here loves to praise, but which has "0" benefit.