Probably back when ME2 was released, took me 2 days to complete it, around 15 hours straight both days. Great weekend, that one.
Same thing happened with ME3, although that didn't take over 30 hours.
krazykidd said:
Only other game i played for 24 hour straight was dark souls , when it first came out .
24 hours of Dark Souls? Even though it is my new favorite game of all time, I don't think I could manage it that long in one session

I think my longest DS run was about 5-7 hours, started a new character, rang both bells and got the Lordvessel. That was a pretty good run, I have to admit