I have the SAME exact problem. Before I started studying for the DAT (which was 2 1/2 weeks ago) I have NEVER studied for more than 5hrs~ in a single day and never for longer than 2 straight hours. I am one of those people that read it once/do one problem once and just wing it on tests and get As. I get sooo bored studying so long and constantly go on FB if I'm on the computer, get up and eat something if I am near the kitchen, take a nap if I am near a bed, or turn on the TV if I am near a TV.
HOWEVER, for the DAT I have upped the ante to studying 3-4hours straight no breaks and up to 8hours a day. I did it like a process...(like you were quitting smoking lmao) aka my first week I tried my hardest to study 2+hours straight and timed myself with my phone and kept telling myself (if I started at 6pm) that I COULD NOT get up until 8pm AND at the end of the day I would tally up the hours in my head to reach at least 5-6hours a day; trust me this was very hard! ALSO it helps if your someplace where there can be completely no distractions like the library very far from the computers (and TV and beds...) around other people studying. For example, I live in NYC and I went to study in the grand public library which is so quiet that I was AFRAID to get up or make noise in my seat cuz people would look up when you made the slightest sound (ya I'm weird like that). O and the guy above me saying to study different subjects at different times is good! For example, I would do 50questions from the DAT destroyer and review the answers and feel so drained but then watch a Chad video because I found them entertaining/amazingly useful when I needed a break from doing problems. I also work better with video>books so this helped me alot when i started to feel bored reading words on paper.
I however, still have never studied for 10hrs+...or ever passed the 4hrs+ straight mark in a single day without getting up to do something non-DAT related aka to watch TV or go on SDN like I am right now... BUT I am proud of myself so far for studying so much, and if I can do it so can you!Hopefully, this is sufficient enough for the DAT...mine is in 9days...I'll tell you if it was ha. Note: it really isn't about how much hours you put in but about if you really comprehend the material you just studied so make sure when you finish studying to do some questions of said topic to make sure you actually accomplished something that day by learning something. (aka I did 50Dat destroyer problems a day and always did Chad's quizes after a video set//still take his quizes randomly from time to time to make sure I retained the info.