so ok, youve made it so we can cut 15 MP off of spirit perpetuation costs, so they cost practicaly nothing to keep out. that still doesnt make them usefull, because last i checked: Summoner spirits stopped getting spells after level 75.
Casting Time = (48 + max Summoning Skill - current Summoning Skill) / 3
so
((516)-(48 + 417)) /3 =17
so a 17 second delay for spirit recast timers, minus 5 for the pants, gives you 12 seconds, sub scholar for matching storm spell, and current day, gives you another -5 to spirit casting time for a total of a 7 second spell recast on spirits spells. now this would potentially be AWESOME if spirits continued learning all of their spells after level 75, or at the very least give us access to the hybrid elementals from abysea.