I figured the implication was that we'd see a year per intermission. Intermission 2 was the end of their first year, so I assume Intermission 3 will be the end of the second and Intermission 4 will be when they arrive.
Intermission 4 could be shortly before the end of the journey, just as Intermission 1 was slightly after the beginning of the journey (in John and Jade's case, at least).
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"One toot on this whistle will take you to a far away land."
-Toad, SMB3