I'm sure you'll get several answers but for us it's been anywhere from 1 and 1/2 hours on a good day to finding out the ferry was canceled, taxi to WE, wait, check in at Cruz Bay, ferry to Redhook, taxi to STT. So anywhere from 1.5 hours to 3-4 hours plus the time you need to arrive at the airport. We love taking a last swim and a leisurely departure but we've had some very close calls getting from RT to the airport - s**t happens! We've always "made it" so far but the worry about a close call can surely zap most of your "island time" mood. I think everyone needs to decide how much cushion they are comfortable with.
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