The "N" you say? That's a tad high...well depends, are you running a large front mount cooler? Ideally the fan should cut in just after half way up the guage (about in between "O" and "R") and should bring it back down to around the "M" about 1/4 mark... roughly.

If it is getting right up the top that seems exsessive, but again if your running a big cooler then it will get hotter quicker and cool down slower (personal experience)

I'd be checking the thermostat is not sticking myself