How long is too long for the little 250?

[IndyKTM]

I bought my 04 last week and haven't ridden a street bike in 10 years or so. I race harescrambles on my dirt bike, so I am used to holding it wide open. I use my GZ for my daily commute to work, it's about 30 miles, 15 miles country roads, 15 miles freeway. IThe bike about 3600 miles on it. While driving on the freeway I get up to around 65 for about 10 minutes. That's not WOT but the bike wont do much more as I'm sure you guys know. Well how long can I maintain this speed of around 65 and feel comfy that I wont do damage to my bike? I saw someone on another site say they had a piece of the cylinder break off and enter the engine which was devastating. I don't want to replace my engine for about 20 years so....

15-30 miles freeway driving doesn't sound like it should kill any road bike but are these things just built like crap?
Anyways, I need an answer to my question about how long can I maintain 65 or so and feel comfortable I wont kill my engine.