Does it creep up and come back down as the t-stat modulates? If it doesn't do that, then I WOULD worry. Sure, it is at an OK temperature but if it isn't controlling as it should then something is going wrong. Is it going to lead to a catastrophic failure today? Probably not. But it is an indication that something in the system is not balanced where it should be.

I'm not sure exactly how, because it really shouldn't matter at highway speed, but I had a thermostatic fan clutch that worked around town but failed on the highway.

Also, I've seen very large variation in the temperature readings produced by various temp sending units. If you, or a friend, has an infrared thermometer -- laser guided temp gun (I have a friend that works in HVAC though I think you can pick them up at Home Depot these days for around $50) then you might want to use it to verify the temps you are seeing. Just because the gauge shows one thing doesn't mean everything is working like it should (annoyingly).