Laptop sometimes sleep into S1 and sometimes into S3 state

I have a laptop in which Windows 7 Ultimate x64 SP1 is installed.
Full system starts take a long time, so I prefer shutting down my laptop into sleep mode.

The problem is, when I try to turn my laptop off into the sleep mode by either the power button, from the start menu, or by a third party application, it sometimes go into S1 sleep state and sometimes go into S3 state (system power states). This has been happening for a year and I couldn't find out what causes the system to go in which state. It just randomly goes into one of these states.

And I should mention this strange symptom: When it once goes into S1 state, it always persistently go into S1 state until I once make the system shut down or hibernate. Using the power button or start menu item make no difference. If the system is fresh restarted or woken up from hibernation, it always go into S3 successfully for at least once. So, when this "being stuck in S1" happens I usually make it go into hibernation once to solve it.

The system BIOS has no power option to choose a stand-by power state.

I want my system to always go into S3 state when I try to put it into sleep.
How do I make this happen and solve this problem?

Bump

I would really like to see any response to this as I have the very same issue on my desktop and it really goes on my nerves when I am about to go to sleep really and after I push the power button it goes to S1 mode instead of S3 as it's supposed to go. It happens very randomly and the fastest workaround is to log off before entering sleep mode again.. this time into S3 finally. How to disable S1 altogether? That mode is completely useless to me.

At least please tell us what debug is needed like powercfg /energy report or something.