I know that coppermine is suppose to take care of generating those files on the fly. However, with some shared host company (I'll point finger here: bluehost), running convert a lot counts against your CPU quota. This is especially a problem in batch upload where even if the original size is small, a large amount of photo would still be bad.
So, is it possible to do convert off line, adhering to the thumb_ and normal_ prefix set in config and in batch-add or would coppermine attempts to run convert anyway even if those files exist??
Yes, you can generate the thumbs and intermediate images on your client as well and FTP upload all files. Then batch-add your stuff. Read up the tutorial "Batch-resizing pics with Irfan View" on the Tutorials (http://coppermine-gallery.net/tutorial/). Just make sure to respect naming conventions (prefixes for thumbs and intermediate images).
On the batch-add screen, coppermine will not attempt to create thumbs and/or intermediates of correspondingly named files already exist.