Migrate until full, wait for mailbox to expand, re-migrate until large mailbox is now full, is the best strategy that we can control.
We have no control over the auto-expanding archives. We are at the mercy of Microsoft to expand those, From what we see it could take up to 30 days for additional storage to be provisioned.
And normally the ODME tool would migrate mailbox faster the autoexpand could do to keep up in real time. Autoexpanding archive would not be able to expand fast enough to keep up with ODME within a single migration task.
If you did multiple delta migrations so that each time the size of the mailbox was over the threshold (90% full) to trigger the auto-expansion, it would get eventually get all the mail migrated over.
You can migrate each mailbox 10 times