When you deviate, your travel can begin up to 30 days before your cruise begins, AND can extend up to 30 days after you disembark, or at least that is what we’ve been told.
We were on the Splendor TA this spring and disembarked in Trieste, traveled in Italy for 12 days, and flew home on Regent Air from Milan to London to Baltimore, all in Business class on British Airways. Yes, we love that British Airways flight from Heathrow to BWI!