The 'turned off' rune would work like saving a file in your video game. Unless obstructed in some way, it may be somewhat faster to mature once returned to. Depending on what stage in the creation process it was stalled at, an idiom may revert to one of many marks, glyphs, or seals, that often serve as its building blocks; this would transform a prep in to a minor action, and weaken its overall strength on that turn.

'Charging' isn't really something that applies to most runes, they need only be written in magical ink, and their effects are almost always consistent from one to the other. Some may be enhanced by increasing their size, and this could be seen as an obvious prep. Applying more runes in a stack could also be seen as a prep... right now, I suppose if there's no boost to how many 'preps' Myron can conjure, then the buff provided by his time paradox is instead a boost to just how powerful his next prep may very well be, based on how many runes he'll stack and abuse on his next... oh god how many times have I used this abbreviation by now... his next prep...