I'd say - Yes. I have both AS & NW accounts, but will probably be crediting all my miles to NW-to consolidate. My plan is to continue to rack up AS miles through varios means (credit card, mileage dining, etc), which you can then use to buy 5,000 mile upgrades on AS or an AS50 award for 15k. You can do this (e.g. upgrade an AS segment that is part of a larger AA/NW itinerary). Since the AS miles don't expire, no reason not to do it. In my case, it allows me a place to put miles after I reach my desired mileage level or elite status on an annual basis on the other carrier.