Someone check my logic?

[Wiregeek]

Or if you wanted to be a complete ass to your PCs, have an older sorceress run out of magical ability... and research ends up showing that she's literally burning eggs to cast.

Which leads almost directly into some terrifying caster-harvesting horror anime wherein young girls are being brought up for the sole reason of harvesting their eggs..
"No can brain today. Want cheezeburger."
From NGE: Nobody Dies, by Gregg Landsman
http://www.fanfiction.net/s/5579457/1/NGE_Nobody_Dies