Various internet acces providers kill process which late too long. 30" is not rare.

E.g., generating thumbnail is known to be time consuming, so one has to list no more than 20-30 images in a row.

The problem is that the simple process of listing the images lacking thumbnails is long !
With 724 images, I can no longer succeded in running the first part of the "Miniature" script.

Suggestion:
these scripts with long loops should be written on a restart-on-error way (like asynchroneous refresh):
this consists in storing from time to time at some logical steps the context of what has been finished and what is yet to be done.
Thus, each reloading/reruning would let the job progress.

--
Fabrice