145.012 spring broken? But why??

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Hi everyone,

this morning I went to the bank to put to rest a couple of watches in my safety box.
Since I was there, I pulled out my 145.012 that was sleeping since late July, I admire it a bit (lol) and I decided to wind it and then after a few turns I heard an unusual sound, like the spring was "slipping". The second hand started to run and everything looked ok. So I left the bank and I didn't bring the watch with me.

But when I came back home I called my watchmaker and he said the spring is probably broken.

The watch worked perfectly and it basically slept for 8 months. This morning I wind it gently.
My question is:
What could have been the problem? Low temperature in the caveu for a few months? Humidity? (btw the watch is wrapped in plastic-clipped-bags and inside the main box there are silca gel).

Thanks for your answer
 
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it just happens from time to time... I had the same with my 145022 without any abuse, but its sucks...
 
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The life expectancy of many mainsprings is approximately 20 years. Many last longer, and some don’t last that long. Metal that is caused to frequently flex can “work harden”, and breakage can result. A mainspring can also lose its hook at the outer end. The type of breakage can give an idea of the cause of the breakage. A mainspring should be replaced (even if not broken) at the time the watch is serviced. I have shown an extreme example of mainspring breakage that crossed my bench recently.

 
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Thank you so much. Do you think low temperature can be a reason (underground caveau)?
 
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My understanding is that springs fail catastrophically in a stochastic manner. It can happen at any time for an aged mainspring. Don't look for causal explanations.
 
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Thank you so much. Do you think low temperature can be a reason (underground caveau)?


No.
 
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I even bought new mainsprings already broken in their unopened packaging, modern and ancient stock. It just breaks when it decides it's time.