You should check to make sure the first fan is kicking on...the second fan is for when you turn on the a/c. The first fan (drivers side?) should kick on when engine temps reach around 190-200....if not, check for a bad fuse, sensor, relay or bad fan motor or wiring/bad ground issues. Both fans should be running when the a/c is turned on. Also, make sure the lower bumper air deflector is not broken or missing which can alter the way the air is drawn through the radiator. And perhaps have the cooling system flushed if all else looks ok...the radiator might be clogged up with gunk over time after 8 years. Changing the t/stat would help also if it is staying closed or only partially open....you can tell by feeling the upper radiator hose when the engine is warmed up and see if it feels hot....if not, change the T/stat.
The a/c is suppose to cycle on and off periodically....you might still have it checked for leaks and proper pressures if it seems to be doing so more rapidly.