Hi Jenny,
This can depend on multiple factors, though the biggest one is the number of voila files provided at once. Are you increasing the core count with -j8 ? The indexing process will only need to be run once on one set of files. There are two ways you can speed it up as well:
--skip-type-indexing will disable the types checkboxes on the index page but significantly speed up the indexing speed.
--memory-map-hdf5 will load the voila files into memory for processing which is a good option if you have the spare memory on your computer to support it. You'll also need to save the index file separately if you do this with --index-file <some path>
Let me know if any of these help, otherwise, feel free to post the screenshot of exactly what the output looks like so I may provide a mode detailed suggestion.
Thanks!
-San