The microprocessor that controls the fans etc is designed to turn the fans on at 55 deg C and off at 45 deg C. You should see the temps go up and down between these values as the fans turn off and on.
Gaming of course increases the heat load. 65 deg C is a bit high which indicates that the CPU is not getting rid of heat quickly enough. This is due to the poor heat conduction between the CPU and heatsink.
If you have removed the heatsink to clean dust from it then just screwed it back in place you are likely to have poor heat conduction.
This is due to the nature of the thermal heat transfer compound or "paste" that MUST be used between the CPU and heatsink. I say MUST because if there was no "paste" there the CPU would overheat very quickly and thermally shutdown to protect itself. It is the thermal paste that provides good thermal conduction between the CPU and heatsink which allows the cooling fans to do their job efficiently.
Sager normally ships their laptops with a metal "shim" (a thin metal sheet) sandwiched between the CPU and heatsink. The shim is glued to the heatsink by a couple of very thin strips of special high temperature glue near the edges. Sager then apply thermal paste between each layer so you get: CPU / paste / shim / paste / heatsink.
Once you remove the heatsink the thermal paste "seal" tends to get broken. The thermal paste will re-seal a bit once you replace the heatsink but it is never as good as an original application. Hence the higher CPU temperatures.
The best way when you clean your heatsink out is to remove the existing thermal compound (and the metal shim), clean the heatsink and CPU, reapply a good thermal paste like Arctic Silver 5 (AS5) and then put back the heatsink. You will find your temps and the amount of time your fan comes on will be dramatically lower. Note the normal temps still oscillate between 45 - 55 deg C as they are the set points for the fans as controlled by the internal microprocessor.
For an excellent tutorial on applying AS5 have a look at the Un-official AS5 guide in the 56xx technical subforum:http://notebookforums.com/showthread.php?t=11362