When you cast spells, there is an initial charge time before the spell is cast. While you wait for the charge to finish and the spell to take effect, you could be getting killed, and losing control of that summon and adding another enemy to the list.

If, during the charge animation, you go into one of the game's menus such as 'Skills' or 'Inventory', a glitch in the game cancels out any charge times and instantly casts the spell.

This comes in handy when you NEED to heal instantly. Cast heal on the person, press Triangle, click on inventory, and you hear the heal spell come out instantly. Try a barrage of fire arrows and you will kill just about any boss.

Its cheesy, and it takes advantage of a game's fluke, but if you need it enough and it means not having to reload 2 hours of gameplay, I dont feel cheap using it.