Runes can either be permanent or temporal. permanent runes, notated with a [P], make a permanent change and, therefore, “holding” a spell cannot be done. Examples of this type of rune are Break and Heal. Temporal spells must be held to be of use. Examples of these runes are Hold and Strengthen.
Time Considerations

Spells take a number of action rounds to cast equal to the number of mana put into the spell. If you were to cast a spell with 5 intensity, 3 range, and 3 radius, the spell would take 11 action rounds to complete.

Spells that are temporal can be held. This is difficult as holding a spell takes lot of concentration. Every five minutes that the spell is held will drain the caster a point of Mana, regardless of the original roll.

In addition, holding a spell takes concentration. Each 5 points of spell being held adds a penalty die to any skill rolls.