The point is that if, as you write, EF did not finish indexing the first time, indexing of a mailbox with 47.510 elements took EF around 10 hours altogether. Because I remembered this thread, in which I/we thought indexing did not finish because of lack of disk space, this is not what is happening in the actual case.
On the other hand, an indexing time of around 10 hours for 47.510 messages is really a lot. And no, the computer did not do anything else as it was not in use. Summing up the whole experience of backing up emails - my primary reason for EF - is rather not that nice:
Importing mail from “Sent” into EF: 5 minutes for about 14.000 e-mails.
Indexing mails in “Sent”: ~4 hours.
Importing mails from “Archive” into EF: 12 minutes for about 47.500 e-mails.
Indexing mails in “Archive”: ~10 hours (and guess what? I opened EF in the background and it started indexing the same mailbox again.)
Not yet have I replaced duplicates (which starts indexing again on both mboxes).
Not yet have I created specific smart folders, etc.
This all on a MBP with a 2,7GHz i7.
Are these really the times, EF needs? Or is there - again - something going wrong?
Added ~4 hours later:
Finally, EagleFiler stopped indexing messages while I was away. (Yes! Hooray!) I closed the library and - just to make sure, EF did not “forget” to index messages - I reopened it:
Currently reindexing of folder “Archiv” is displayed with an estimated time of 74 minutes (message 2000 of 47500).
Estimated indexing time raised to 2 hours, 33 minutes at message 3778 of 47500.