If you think about it, the world he and his wife were in for "years" was supposedly at least a few levels in, right? And they were obviously still using their own familiar places at that time to construct their dream worlds. That's why he stopped doing that after his wife freaked out about it not feeling real. The problem with them experiencing years inside the dream is that when they 'died', they weren't shown waking up through several levels. Just one. Maybe it was meant to be implied, but if they spent years down there, what are the chances that they actually got all the way out? Maybe his wife actually did wake herself up.
The world they were in is just "limbo", or the collective unconscious. I believe that Cobb mentions or alludes that killing yourself in that world wakes you up to reality, so you skip other "levels" of which are different than limbo in that they are dream-states. This is why it's still safe for Cobb to go after Seito after saving Fischer while everybody else gets kicked back level by level (which is why Ariedne says "he'll be okay" to Arthur).