I have used import tools from other forum platforms with similar amounts, never takes more than a few (3-4) hours at most. Importing from a Xenforo installation of a similar size to IPB 3.4 was quicker than even that.
I know it's not my servers resources as as even when I boosted the rate limit to 9999 threads (from 100) and 99999 posts (from 800) it's still using less than 10% CPU, all other resources are under similar usage, nothing near maxed out. However, even with the rate limit increase to that (I even double checked by closing the import page, then re-continuing it) it doesn't seem to go that fast, it's only increasing 0.03% - 0.06% every 10-30 seconds. Is it not able to handle that much at a time or is something else wrong?
Anyway to speed this up in the future? It recommends you close the board for the day when doing this, keeping it down for a whole day is really bad, especially for larger boards.
Does completing the import take awhile either? If so, anyway to speed that up? (if it updates the index, cache, etc.) Or can I at least reopen the site while it re-indexes the new content?