To much attic exhaust venting? Help check my math
You can never have too much attic vent.  If you have proper insulation installed,  with vapor barrier, there's no problem with heat or moisture loss from the house proper.
The roof itself is 'happiest,' i.e. will last longest, when the underside (in the attic) is as close in temperature as possible to the top, exterior, side.  That's why attics are supposed to have full airflow from outside the house.