It is different for each person. For mine last date of travel is July 1, 2010. Just must be redeemed (ticketed) by Feb 28, 2010.

So this morning I called back as still wasn't reticketed. As expected, this time the agent told me what I was told a few times before (but not yesterday): that reticketing absolutely, categorically can not be done - and is never done - until day of flight at the airport (and thus no OLCI) and handing in some piece of paper. I explained to her that these electronic (not paper) PU503s must be ticketed by Feb 28th, and that by May they will have expired, while the fly by date of July 1st will be still valid, so I do need to get it reticketed now (preferably today while I can still see their status online at nwa.com). She called the ticketing office in Salt Lake City and after a while told me that she got someone there to take care of it.

Then afterwards to my surprise a few minutes later I got a call back from the ticketing agent in SLC who said that he can't do it today, but that he'll do it first thing tomorrow morning (as apparently by tomorrow DL will be able to see and use NW ECVs). So, ^ for that. I'll see tomorrow morning is it actualy properly done by then, but I definitely appreciate the ticketing agent calling me back (at NW I recall that I was told that "no one may ever speak to ticketing" or something to that extent) and offering to call me back tomorrow morning to confirm that so is done.