For How Do You Press the Power Button Before It Starts?

Hi. When I press the power button of the iMac late 2009 i7, it sometimes doesn't start. How long do you press and hold the power button for it to start right away? One second? Half a second or fast and immediate but firm. Is there like a delay when you press the button (to prevent accidentally switching it off I suppose) like it is when you press the power button on cellphones? Or is my iMac power button, power supply or logicboard defective? (I do use an 1000w AVR with a surge protector plugged to it). Does the Mac not chime immediately? There's a delay of 8 seconds after I hear the chime after I hear that electricity sound (like a hizz) when you have powered on the iMac. What may be the cause of this iMac being hard starting (I shut it down when I'm not using it for 8 hours or more, sometimes if I'm not going to use it for 1 to 3 hours also). Thank you in advance.

Gbu,

Alvin