From a wider viewpoint, this spell doesn't let you break spells-per-day economy. If an enemy takes fifteen Scorching Rays to kill, you're going to need to cast 15 Scorching Rays one-by-one, whether into your foe or into your Spellblade network. This trick doesn't let you get extra spells per day, which is what I (confusedly) thought at first with the whole "millions" number being thrown around.

(Seriously, think about how many spells per day even a Wizard20 gets, then think of a million. You'll probably never even hit 100 "unused" (and then stored) spells during standard adventuring.)

That being said, it does let you break action economy in tactical combat with preparation. Firing your full allotment of spells-per-day (and possibly then some if you had extra spells the day before) within a single turn is still mighty-fine. And by mighty-fine, I mean that's how your enemies will be after that single turn.