Spell rules count only 100 i thought, but DSG is the spell mod. And if a spell can handle 100 casts it can also handle 500 (if not limited by using more array places on one cast),,
EDIT: You can use about 16 array places per cast to make it still MUI with 500 casts,, (about, i rounded the array number down to 8190 and i rounded the value down, to 16),,