Consequence of running GPU overclocked 24/7

[Kaiju]

I was just wondering what factors I should consider when running my GPU overclocked throughout the day.

Will it add more to the electricity bill, will it be able to run on stock fan speed when it's not being stressed in 2D?

I currently use Rivatuner profiles for different apps, but was curious.

 

[Kaiju]

I have a 9800GTX+ using the following profiles.

2D it's at 370, 920, 550 (1100)
3D it's at 800, 1910, 1240 (2480)

Stock is, 738, 1836, 1100 (2200)

So you think I should undervolt it even further for 2D?