Basically, we don't know anything except that she's not addicted, like Eluvianix said. So presumably there's some story reason behind it. Maybe the abilities aren't the same. Maybe only some abilities require a lot of it, and others don't. We know Alistair quit and started again, so maybe you can... time it. Too many theories without more info.
But it's very... suspicious.
Coming back to Cullen, our best comparison is not so much Cassandra but Evangeline, to my mind, who definitely needed it regularly. So... I reckon Cullen will, too. I'm not too concerned on that front, altho more info is more.
My best guess is that the Seekers, like Lambert and Cassandra, still require lyrium for their powers to function, but at least the upper echelons of that Order have found a way to circumvent the addiction part. How they do it, I don't have a clue. The method by which it is done is probably something the writers created.
Either way, Evangeline, a top tier Templar, could go for a week without the need to ingest the substance. I roughly estimate that she and Cullen are more or less the same in terms of ranking in the power hierarchy. Therefore, I think Cullen would require lyrium probably as often as she does, if not more.
Retour en haut
le-gasp! XD
That's how I'm making a Cullen cosplay for my boyfriend to wear. My boyfriend agreed to cosplay as Cullen to ECEE 2015 after I pointed out that they look really uncannily similar. 
