Is their a published source for this information? I think it might be important to know how long they live.
If they run into our party in Counsel of Thieves, the answer would appear to be 'not long'.
More seriously I think they age and grow at the same rate as the base race, as they have only a fraction of outsider blood.
I believe the 3.0 supplement Player's Guide to Faerun has age information for planetouched races, and the 3.5 Planar Handbook may as well. There are no published Pathfinder sources, however, as they aren't officially player races in Pathfinder. Using the stats for humans seems like the best and safest bet. Perhaps add a few years to each category, but nothing dramatic.
Perhaps the mortal sides of them slowly ages and whithers away leaving the small outsider part behind in the form of an imp, mephit or lantern archon?
The few sources I've seen have them using the same vital information as humans, including height, weight, and age. They had charts in the Races of Destiny, but they were pretty much the same as humans.