BoM/TWS Message Forum

It's commented on that most are found by about the age of 10 at the latest. Eldibria has been suggested as being harder to track down, so might take longer (it's also been suggested that one reason why Rick is so messed up is that he wasn't spotted till he was older)

Sulvae you have to literally stumble across to find (the fact that Will manages to stumble across almost all of them should be noted down as being really freaking wierd)

Logically Sulva and Eldibria would be the hardest of all to find. As it happens that's one of the few combinations that hasn't been identified in story.

Other reasons for a delay in finding might be a lack of resources, or jurisdiction friction between the three Stellae like groups