Default [Q] overclock frequency not sticking- is this normal? Help pls

Hi guys. Im new and i need help. I game a lot on my gs3 and usually overclock my device. One thing i noticed is that when i overclock to 1.6mhz to 1.7mhz, it would stay there for like 5 minutes, but then the device gets slow and when i check the frequency it be on 1.0 mhz. I'm using a gs3 i9300 tried both setcpu and no frills. Im on latest siyah kernel running stock samsung rom. Thank you very much. (did i do this post right, is this the right section?)