How many hours can you stand facing your computer?

Hello guys..when I had online job before the number of hours being required by my employer was eight hours. Honestly, I couldn't stand that straightly, I did some breaks in the middle of that 8 hours. I don't remember I was able to work that 8 hour straight of online work. Does anyone here can work on that length of time on online their task? (excluding of course on our meal breaks)... Mobhomeir here 070912 0946hrs