If you download a WU and it takes a year to complete it, the data will still be added to the database and it will be available to researchers at that time.
Note too that there are two deadlines
, a reassignment deadline and a final deadline. You definitely get the points if you return the WU before the final deadline, even if it has been reassigned to someone else. I am still looking for the answer to whether points are rewarded to WU's submitted beyond the deadline, but I am guessing the answer is no.
Every WU is important, and, with the possible exception of the deadlineless WUs, a new WU is generated from each one as it is returned. That's why we stress "Don't delete WUs"
Every WU is unique (only issued to one person) provided it is returned by the deadline. When you fail to return something by the deadline, the system assumes it has been lost and reissues it . . . until someone actually returns it. If the same WU is missing several times in a row, a portion of the project is delayed several multiples of the deadline. . . still waiting on somebody to complete it.