Originally Posted by FCYTravis
Just remember that status-matching is usually a once-in-a-lifetime type deal. Do it once and you've used up your shot at that airline.
There are likely ways around the once-in-a-lifetime stipulation, but they're probably not worth the time.
E.g., you get comped NW plat from AA EXP. You maintain AA EXP but lose NW plat. But the next year you're going to fly NW a lot and really want plat again (and you'd rather have NW plat than CO or DL status). So you use your AA EXP to get comped to US CP and then use that US CP to get a new NW account (with different address) comped again to NW plat.