As soon as he's said you can do minor things like that Promise construes storing her hearing as being ever so similar to fairy lights. They are both easy accessible magic that she can do right here and now.

She doesn't want to miss a useful caveat, but he says "as long as", and then she stops hearing him until she sees a pause that looks like it's probably between sentences.

He's talking about writing implements. Good.

She sits. "I'll get started."