Fucking IDIOTS.
"I know, let's make him live out a bajillion years of mental time."
That'd be fine if he was a Fighter-type. BUT HE 'S A FUCKING MAGE. KNOWLEDGE IS POWER. Cultivating mentality, increasing comprehension, boosting intelligence, training knowledge of magic through mental simulation and experimentation = EXTREME INCREASES IN MAGICAL ABILITY.
You turned him into a fucking god! Should have just stabbed him in the dick and heart a few times before incinerating his brain!