That makes sense. Thank you, wwjd0691. In the end of my 5-day rebooting test ( http://bit.ly/GGLIME_newthread ), I powered off my PC with "hibernation" mode. The reason why I did it was my experience in testing Build 551 - sometimes, I used "hibernation" and recognized that 4-hour limit did not occur on my PC until I totally shut down my computer and restarted. Because I remembered it in somewhere in my mind, I powered off my PC with "hibernation" this time. Well, then, your comment above made me sure the reason is the "hibernation". Thank you, again. I will keep the hibernation to continue evaluation of RC (Build 553) until a further announcement of license key is released by "Andrey" or I have to reboot my PC for some reasons. [Bunji94 form Japan, with solicitation to wwjd0691`s comment]
P.S. Other testers, if your RC is on the last day but you want to keep testing the RC, you have a choice to power off you PC with "hibernation". You may continue to test RC (Build 553) .....