iMac overheating. Take imac in store?

I've had my 27" iMac since 2010, after 2 years I suddenly noticed heat. It heats up so much it makes me paranoid.

I have smc fan control installed, and it helps, but I know that upping the fan speeds can risk the life span of my hardware (fan). So I use it conservativly. I'll probably buy a desk-fan next week. It seems like a quick solution to a worrying problem. Do all apple hardware end up with this problem? is it dust? Blocking the vents. General ware and tear? I don't really want to shoot/suck air into places that might mess up the computer.

Is it worth taking into the store or will I just be told to change the fan speed. Can they fix it, because it never used to do this...