It sounds ridiculous now, but consider that when it was first put up, the Eiffel Tower was meant to be a temporary structure for the World Fair in 1889, with the term giving Eiffel the rights to commercial exploitation of the tower for 20 years, after which it was meant to be taken down. The terms required the tower to be build to be easy to dismantle.
Even though it was decided not to take it down in 1909 when the rights reverted to the city, it was not a given it would remain up permanently.
I have a friend whose family owns an apartment next to the Eiffel tower. Apparently, her ancestors got it for cheap because people were afraid the tower would fall down and nobody wanted to live next to it...
Which makes me wonder how long it will actually last. The last time I was up there there was an awful lot of flaking rust visible on parts that - to me - appeared to be structural.
My impression is that surface rust tends to form a protective layer that prevents deeper rust, so sufficiently massive steel objects aren't in much danger. I could be mistaken.
Yes, hence I mentioned flaking rust. Surface rust, if properly treated can indeed protect deeper layers, more in other metals than in steel but it is a well known concept, a protective 'skin' that prevents further oxidization. Flaking rust is when the rust splits of layers of steel, typically seen in steel that has been 'folded' while being forged. That's not a good thing, it allows water and air access to those deeper layers by creating space where the rust has pushed away the surface layer from the deeper layer.
Even so, those elements the Eiffel tower is made out of are about 1" thick (25 mm) at the base of the tower and there is plenty of redundancy in the design so it's not like it will fall over next Tuesday.
I wonder how you'd tackle repairing it, those are for the most part forged rivets hot joining the steel elements, you could drill them out to replace an element but that would have to be done extremely carefully to first take the load of that element with temporary bracing.
I'm pretty sure the city of Paris will do a lot to keep their iconic landmark, but this will be an expensive operation.
and, to add, it was made of recycled metal. I read that on the sign while on the first platform. The urge to go up further did not increase while learning about that :)
Even though it was decided not to take it down in 1909 when the rights reverted to the city, it was not a given it would remain up permanently.