My scent glands are mostly fine, though I appreciate your concern.

The prep system isn't really based off time, no, it's based off power. It's why when you're talking about magic you can use the term 'charge' interchangeably with prep. Your character is limited by their tier in regards to how much sheer power they can manifest in a 'turn', speeding up their actions doesn't change this hard-cap, in my opinion. You could certainly cast more spells, but they would be weak. The advantage you do gain from that though is that you simply have more spells, so while they may be defended against fairly easily with counter magic, they could hit an opponent with various effects at once, and perhaps sneak past their defences by attacking from multiple angles. (This is where logic and tactics rules.)

The reason why preps can't simply be linked to time is that it would make a character with one chargeable ranged attack with immense speed the most viable character in RP fighting. They can simply sprint far away from their enemy and charge up an attack in the time it takes an enemy to arrive. (Though to be honest, you can still do this.) Also, there's really no good way to dictate how much time would constitute a cap of power being reached. 

The prep system isn't perfect, I'm the first to admit it, but a multi-prep system seems to just exaggerate the already present problems with Preps. I'm not fond of high tier fights for this very reason.

Point being, I think your time spell should allow you to cast quicker, why not, but I don't think this should equate to you gaining multiple prepped attacks. You just get more normal attacks. For example, if you were using a sword and cast this rune, you could launch four or five thrusts in the time it would normally take to launch one. You don't need a magical prep bonus for those five thrusts to be better than your ordinary one. Now times that by about a million, because your character is using funky delayed ranged magic super attacks, and you can see how multi-preps are really unnecessary here.

That's just my take on it, I'm still interested in reading this fight and I'd hate to see it end over what I fundamentally believe would be a mistake, AKA changing to a multi-prep system.