250 Cruisers top out at 70-80 . . . the 250 sports do 100 mph, 65-70 is under 70% speed. It likes to run. Change your oil regularly and it will be good for 100,000 miles no problem.
YOU might have a problem, the smaller bike has higher rpms and more buzz on the hands/feet.
250s today top out at 70 or 80 mph, but they're not designed to cruise at those speeds. For one thing, the engine is just beating its little heart out. Also the suspensions of these bikes are not designed for that speed, so they're not as safe or as comfortable as a bigger bike.
If you're just going 5 miles or so, you can deal with it. But if you plan to do long cruises at 60-70-80 mph,
I would say you need at least 500cc. 650 is better. And that's not that much bigger or heavier than a 250.