FAQに書いてあり申した。
Copy any file into your SETI@home Data directory and rename it
"stop_after_send.txt". On the Macintosh, the "SETI@home Data"
directory is in the Preferences folder, inside your System folder;
on UNIX and Windows it is in the same directory as the executable
file SETI@home.exe. If you later want to get a new work unit, remove
the "stop_after_send.txt" file.