I see trouble with this TBH, 100 is a good number it can broken down into %, tens, singles, quarters, halves, thirds.. etc.
Very easily, it defines advancement, keeps things simplier to create and use.
Allows players to track to minor degrees what effects it has, its use in game.
How much a gain you gain on leveling, where they need to focus in.
Stops the Skinner effect of the need to constantly rush through button bashing for that next rush of pleasure.
Caps are good, they also allow a leveled envioment to match better, allow you know you're a master at something.
Stop you from becoming mindlessly getting overpowered by ignoring other game features.
Honestly it's easier to just reduce cost of spells, make their effectiveness increase and limit underwhelming overpriced effects.
The other point at some point the game just won't cope with adding more and more effects to the player.
I still remember when I modded Baldurs gate 2 to give me thousands of spells, the game pretty much broke.