Can an old mainspring be the main reason for low power reserve in automatics?

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First time I hear mainspring should be replaced at every service. I don't think I agree... unless service is done once every twenty years or so.
 
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First time I hear mainspring should be replaced at every service. I don't think I agree... unless service is done once every twenty years or so.

It’s common practice. Done by every watch brand service centre on the planet, and by most watchmakers I know...of course there are those who don’t, but in my view they would be in the minority...
 
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Here a 20yo main spring from my recently serviced Monaco.
Just giving this thread a visual.

Yikes...that is one seriously twisted up spring!
 
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For the technology junkies here, how mainsprings are made: https://www.thenakedwatchmaker.com/making-mainsprings

IMG_8123.jpg

Fascinating!