Hi,
here is what I used in last project for about 10 000 pages and and it is very simple and basic script.
It's read csv file line by line and create pages, but to avoid execution time limits and to get some other options (eg. "pause" option and later "continue", real-time monitoring, etc.) I use very simple Ajax loop.
Here is attachment and inside it is some "how-to" txt file.
unzip-and-place-content-inside-templates.zip
Please note that I use this for ~10 000 pages (in my case, processing time ~1s/page) and for more than that number you can try to do some optimisations and test it. There are few places for that. Teoretically it can works few days, but is it worth? ? Regards.