I was fairly relaxed about running in my G5. I kept below half throttle, but wasn't obsessive about keeping below forty mph. Occasionally it would creep up to fifty mph in fifth, which is pretty low revs on a flat road. After the first 300 miles or so, I regularly cruised along at fifty in fifth, sometimes it would stray up to fifty-five, but as long as the engine was pretty relaxed so was I. I didn't take it to seventy until I had 1000 miles on the clock, and then only briefly because I was on that kind of road.
I don't think I'd have fancied a 750 mile trip until after the first 600 miles, and probably wouldn't have ridden the bike for more than two hours without a cool down stop.
The engine is WAY smoother after the first 500 miles, and more so through to around 1500, and the sweet spot on my bike is around 58mph. I'm hoping to lift that to at least sixty with the Goldie exhaust. That's not to say it's too shaky at seventy - it isn't, but it's starting to feel a little bit light. It'll do eighty and still has a bit more, but you know you're pushing it, and best to check the nuts and bolts after.....
I regularly do 150 mile trips since the run-in period, mostly old roads at fifty-five to sixty, occasionally a short stretch of fast road at seventy when unavoidable, and a stop for coffee along the way. Average about a thousand miles a month since new. I never worry about it and would take it anywhere. Good bike. Old style biking for sure, but if you're in no particular hurry and into it for the ride I reckon it'll take you anywhere without complaining.