Up to 4 or 5 years ago I used to do long distance trips at "70"cough mph. Always a tense journey on the look out for patrol cars and incidents ahead. Then - and I don't know why - I decided to trundle along at 70. Waaaay less stressful journeys that didn't take all that much longer.Start off on a 300 mile trip, 56mph, tucking in that 1 mile gap inbetween a couple of plugs of lorries........ eta on the satnav - 3pm, music on, relaxed.
Drive for 150 miles like that, then put your foot down and drive like a d1ck.........eta 2:55pm
You'll probably find you've shaved off no more than 5 minutes, get there jangled up and a couple of gallons lighter.
Unless you're driving on empty roads in the middle of the night, you'll never get there much quicker........
As for driving at night. If you go long distances on the motorway and trunk road network you will almost inevitably come across night-time roadworks, sometimes even full closures that find you sent off into the sticks for a few miles.