You never actually see any mages. But no. You mage count stays the same as long as you have money to pay their upkeep at the end of the round.. What happens is that everytime you use a mage your overall mage Mana drops and it refills faster the more mages you have.
[edit] just beat stage 41. Have 250 workshop dudes, 750 archers, 110 mages, and castle strength 400,000. Takes 184500 to upkeep that many men and I still gained 209060 points that round. Glad you got me playing again those little buggers are starting to run fast now.