Thanks for your answer.
I use my N8010 unplugged during some live performances.
The problem happened during my two last performances.
Yesterday I tried to keep my N8010 awoken as long as I can, the display didn't failed but the N8010 was plugged.
I will try another time unplugged and I will tell you.
I tried my N8010 unplugged, with the screen almost always on.
About a certain time (several minutes, generally more than 10 or 20 min), the display turned off by itself.
So I had to put the N8010 off by pressing several seconds on the power button to reboot it. The display and the N8010 then worked well several tens of minutes time without problem.
I also tried on another N8010 with the same ROM: same problem.
Conclusion: Sometimes, the N8010 can work several tens of minutes time without problem but then comes the time when the display turn off.
I didn't find the event that could put the display off.