There is no way you are only getting 40 celsius under load at 5.0GHz unless you are using some form of exotic subambient cooling, or you live in a cold environment and literally put your PC outside in subzero temperatures. If you have an AIO water cooler, then you may see deceptively low core temps initially when testing, but those will gradually creep up as the water heats up and the loop gets saturated with heat.
As for whether to push further the two big questions are: What is your current core voltage? If you are already at or close to 1.4, you don't really have any room left to go higher without pushing voltages that will rapidly degrade your CPU. The other is temps, if you are getting above 80 celsius, you shouldn't push any...