You need to vary the plan IMHO. I'd rather ride a bit longer or stop shorter and stay in a town with a bit of life than sleep in some industrial estate motel. I will do 1000 mile runs in hours rather than days if pushed and it's the only way to get where I want to go, but this isn't fun and is actualy no quicker when you are fit for nothing on the third day. Fine if you sleep it off back at the office or on a ferry, pointless it you waste you trip. There is also usually no real problem with arriving early, you just replan and push on or have an extra beer. Arriving late because you failed to account for the possibility of a road closure or a puncture usually starts a sequence of events that just starts to ruin things, you'll hit a rush hour, the hotel reception or restaurant will have closed, they'll have locked the campsite gate, the boat will sail early because of a rough sea and so on.
I work on 8 hour days with tea breaks and lunch and sightseeing at anywhere good I pass and an average speed of 45 mph. In winter I also work to the sunset times, better to do a short cold dark bit before the first tea break and another later than be out for hours in the evening rush with a filthy visor, a rumbling stomach and head fit for nothing but sleep.
If doing anywhere with manned border crossings I like to hit them mid morning. You don't have to sleep too close (high prices and crime) but the guards will have had their coffee, sorted the early rush, but not yet be in a mood to say ***** it and go home. Worst that happens is that they delay you into lunchtime and you have to hang about while someone eats.
Groups of more than three bikes will always be running late unless you really plan carefully.
Andy