Honda CBR250R red line reliability?

Heres the problem-how well built is the engine?-I have heard that the bike top speed is no more than 90mph but the reason I ask is because wether I get this bike or the CBR929RR am going to be riding around a lot especially long highway journeys. I would add a high air flow air filter and an exhaust system to the CBR250R so that would be a noticeable power increase for this particular bike I'm sure but IS IT OK TO KEEP IT CLOSE TO RED LINE FOR HOURS?

Having owned a CBR250, 90 is pushing it
No it is not oj to run close to redline for hours, cruise should be about 1/2 to 3/4 redline

The short answer: no, you should not keep it near the red line for hours.

The red line is the manufacturer's absolute highest RPM you should obtain. This exists for several reasons, not the least of which is that some of the moving parts will be moving too fast to keep to the right timing. This also adds extra wear and tear on the engine to be near the red line.

In your case, keeping it near, but below, the red line should be kept to a bare minimum. The engine must work very hard at that RPM and you will wear out parts a lot faster. It won't just die suddenly and quickly, but it'll hasten the need to replace things. You don't want to be stranded on one of these highway journeys with an inoperable vehicle.

LOL - where exactly are you, that the cops won't notice someone doing (at least) 20+ mph over the speed limit?
If you're going to be doing a lot of long highway miles/long trips, I think you need to move up from a 250.

I have a rebel 250, and anything near 80, I can tell it's nearing it's top-end.

Wait… 'whether I get this or a cbr929rr'

You are comparing chalk and cheese when it comes to these bikes.

The 929 will be faster, smoother and more suited to high speed cruising.

Even when you modify the CBR250, it won't cruise much better. What makes you think that adding a filter and exhaust will make a 'noticeable difference'? It won't add a great deal - maybe 3-5bhp at most? The biggest difference to cruising you can make is to alter the gearing. The easiest way to do with is with the sprocket sizes.

To answer your other question, the rev limiter is set by the manufacturer to preserve engine life - and prevent it from exploding/bending valves. This is normally set conservatively low, so in theory it could rev higher. Keeping an engine close to the rev limiter will use more fuel, probably burn oil and in the long run will have a bad effect on the engine - although it wouldn't be immediately obvious.