Persistent transients

Hi
Thanks for your excellent plugin.
I have randomly stumbled on an issue while trying to debug something else. Using the Transients Manager plugin, I found thousands of transients with no expiry set, and names like:
finish+/tmp/orders0QVde2
partial+/tmp/orders0QVde2
start_estimate+/tmp/orders0QVde2
with different random characters at the end of ‘orders’.
These appear to be generated by your plugin every time we download orders.
They are building up in the database because they are not given an expiry.
I think they should probably expire after a few hours, 24 hours at most.
Best regards,
Ben