We used to fly around 1000 feet too simply because we were map reading from point to point. At the time the Tacan had a coupling error so was always 40 deg out.
We could have gone higher but there was no point. As for speed OTOH we once did 250 kts from Colt to Gaydon but that was when most large airfield had a BoB day on the same day in September. It served as a marker to the public; they knew when there should be an airshow or the airshow reminded them of BoB.
Now air shows are simply a summer day's outing.