Why is ISS lifespan only 30 or so years ?

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Also, realize that most sophisticated machines have a limited lifespan. How many 30 year old cars and trucks are still out there. Most Navy ships are replaced within 30 years. And they are easily repaired and upgraded, at least more easily than the ISS. How many televisions from 1990 are still working in homes?
There are wires and stuff running through the occupied spaces. Not to mention the stress that the infrastructure must be subjected to, every 45 minutes it heats up to higher than water boiling point then cooled off to way below freezing.
Here are NASA and GAO numbers:

Original cost of Hubble in 2019 dollars - $4.303 billion.
Not Yet Imagined: A Study of Hubble Space Telescope Operations (nasa.gov)
See page 345

Cost of first 4 servicing missions $1.4 billion to $2.6 billion
(Does not include the 5th servicing mission in 2009)
GAO-05-34 Space Shuttle: Costs for Hubble Servicing Mission and Implementation of Safety Recommendations Not Yet Definitive
See page 6
I will accept that as a better source than what came up with my internet search. It doesn't change my view that reliability, durability and disposability are better than repairability. A second Hubble would almost certainly have gained in reliability and durability and probably at reduced costs - from what was learned along the way. The initial screw up with the mirror made wrong for one would be unlikely to happen twice.