Not really. By "around 7 years" I meant rough numbers with a very broad standard deviation. Facebook might be actually 10 years old from first run, but from general social awareness thereof to now is closer to 7, with a tipping point clearly having been reached between young users increasingly heading elsewhere and a growing sense by participants of "I don't want to be here but I have to". Yes, Facebook may have more staying power just because it has hit a billion users and is getting integrated into other devices, but I still see it matching the standard (if a bit elongated) pattern of social media site lifecycle. Those billion users are finding it's hard to be meaningfully social when lumped in with a billion others. Those FB-integrating devices can and will jettison FB on a moment's notice.

In 46 years I've seen a lot of "but this one is different" claims in a lot of subjects. No, it isn't in most cases. Google, yes, is different (but even they need be very careful). Facebook isn't; users are finding they can go elsewhere.

You can look at Facebook as having launched independently in a number of different markets.

Initially it was Harvard (2003), then Ivys (March, 2004), then selective colleges, then all edus. It then tapped high-school students (September, 2005). It was opened to the general public in September 2006. Introduction to other countries also generally came later in the game, and FaceBook have had to compete with alternative networks, particularly in China and Russia. (Most data here from Wikipedia's Facebook article).

It's helpful to look at each of these as a somewhat independent social network.

We're hearing now about significant defections (or failures to join) in the < 25 market. Facebook's growth overall in the US peaked ~2010-2011. It's been growing outside the US, but that's a much less lucrative market for advertisers. Breaking out growth / user patterns by introduction point would be particularly interesting as I suspect this would model earlier social network growth more accurately.

All the other social networks were growing right up until they didn't. They had a similar percentage of the online world.