"I feel like Mages age slower but I could be wrong."

He's... he's [i]your[/i] mage. I'm leaving the details of his race up to you, just make sure I know what I need to know about them.

If you want certain types of mages to age differently, then go for it! Just adjust your "Actual Age" and "Appeared Age" accordingly, and throw in a note about how their aging works so I know in case I wind up with some background elemental mages, so I don't step over the rules you've set for your character.

Forgive me if this is rude to ask, but are you not used to creating your own races, or tweaking pre-made ones to fit your wants and desires?