YVR-SEA AS redemption only made sense when I was booking a last minute flight and the one way would be $300 vs. the miles price at 12.5K or so (even then, not that great of a redemption vs. long haul J). But given there's no longer any cancellation policies, now I tend to just book a handful of dates at ~$100 each way during a fare sale and then cancel/redeposit into my wallet as needed. Alternatively, its 7500 Avios each way on this route, but taxes out of YVR will be ~$60 vs. ~$6 out of SEA.