No, they do not have a time limit or expiration. Do not worry if you think an older PC is taking too long to complete a Work Unit. It will be properly credited to your SETI account and to the Team no matter how long it takes.
From The Berkeley SETI FAQ:
What happens to work units that never get returned by us? Are they lost forever?
We keep track of every work unit that goes out - if it is taking too long getting the results back, the server will automatically send it out to somebody else. Only after we get results back and confirm them we will remove the work unit from disk.
If you don't get a result back from one PC how long does the server wait until sending the same data out again?
For quite a while now we have been sending the data out multiple times over the course of a day or so without waiting for a result at all. That allows us to delete the file from our local disks sooner than we otherwise would (as soon as we've received at least two results) and keep our splitters generating data files at a high rate.
by Doctor Olds edited by samburgers
last modified: 2002-08-17 00:23:32