interesting. thanks for the tip. i went to both sprint's and nwa's websites . . . neither one mentioned anything about this. then, i went to: http://members.xoom.com/_XMCM/sdi1moox/
and found a link to get up to 27,500 miles on nwa by staying with sprint's plan for a year. of course, since you get 5,000 miles after the 1st, 3rd, 6th and 12th months, one could always bail out after month 3 and get the same amount of miles as originally listed above.

i signed up that way, and the links all worked (i.e., nothing about an expired link, or a "you can't access that page" message).