3 hours is a feasible time, although chances are he is lying anyway.
There are some guys who are finish rather quick, others who take a bit, and a few who know how to really last.
I fall into the last category, I can explain why but its probably way more info than anyone cares to know so I'll leave it out for now.
Normally most guys will last about 10-30 minutes, this is probably the best way to go in all honesty (sadly I rarely finish that quick) because as much as they bitch an moan about guys cumming too quick girls really cant last that much longer either. Girls say they can go for hours, but trust me, they get sore and worn out just as easily no matter what you do. If she isnt satisfied in at most 30 minutes you are doing something wrong.