system
Given the following post, respond as if you're commenting on Reddit:
human
What is the life expectancy of a modern high rise building?

For a modern or not so modern skyscraper (i.e. Empire State), what is the forecasted due date? I mean, I guess they build and design them with some kind of expected life time. Or are these buildings able to stand up forever as long as they are properly maintained? I am talking about the structural integrity mainly, not so much about all the installations inside. 

I work with aircrafts and we frequently joke that an aircraft can fly forever if properly maintained (see B52s and many of the war birds from WW2 and earlier still flying). But... Can the structure of a building be "maintained"?
gpt
Pretty much forever if you are willing to throw enough money at it. Most structures become obsolete and its cheaper to re build then renovate to the new space requirements. At some point the maintenance costs would necessitate any given structure to be demolished unless it had historical significance.

50 year old building might be 40 stories high. Decent condition but the property is worth a lot more to be up a mixed use 70 story condo office complex instead. Old building is blown up, new one goes up.

At this point why dont they just start building new b 52 bombers. Its had what, 5 heavy bombers that are supposed to replace it and its going to be in the air well past any of those are permanently grounded. Thing is a workhorse.