for how long can u sit on a chair at a stretch!!

Bad concentration has been very difficult for me to counter since quite some time now.....no matter how hard I try it usually was always difficult for me to concentrate for long...... The longest that i concentrated was about a year and a half bac when i sat in the university library for 6 hrs continuously and studied...I thought that was once in a blue moon occurrence as otherwise i cant concentrate for more than few hrs......but last week I was online for 8 hrs and 40 mins!!! well itz tough to believe but thatz wat happened...i didnt get up from the chair for even once....no break of any kind at all.....well it had a positive rub off in the sense that i actually believed that i can still sit for hrs and concentrate......so thatz wat i actually managed to do today....studied for 5 hrs at a stretch.....o' wat a feeling!!! I hope this trend continuous....and when will i go visit phagwara...i should have gone last week......but somehow i am still in chandigarh..... :-)