I think the belief that a schedule is dangerous is one based on insisting on leaving at a given time or date irrespective of impending weather but of course one has an expectation of the duration of a trip/voyage.
On a crossing I budget 150nm a day and generally try to achieve that even if quiet periods mean a little motor sailing. Thatís a nudge over 6kn average speed. Iím not one to sit around drifting when the wind goes AWOL. After all, we have to charge batteries or run the water maker now and then.
I try to never beat on a crossing. If I had to develop a polar for my boat it would ignore anything forward of a tight reach. I run a 135% genoa until the wind gets back to the quarter then if AWS is 15kn or less the gennaker goes up.
I met a German fellow cruising many years ago who said that when his decks got wet he knew he was doing it wrong