Most of the WU have run times of about 1 minute.

But there are 2 types of longer WU, both with an error.

1. WU duration of about 1500 s:
<message>
upload failure: <file_xfer_error>
<file_name>wu_47880434041236_22_0</file_name>
<error_code>-131 (file size too big)</error_code>
</file_xfer_error>
</message>
and in the BOINC log you can see:
15-Feb-2017 13:56:30 [nanoHUB_at_home] File size: 64439496.000000 bytes. Limit: 50000000.000000 bytes

2. WU duration longer than 4000 s:
<message>
exceeded elapsed time limit 4332.09 (100000.00G/23.08G)
</message>