ECTS time validity and expiration
I'm pretty sure that this depends less on the ECTS system, and much more on your specific university. That is to say, I assume there is no general answer to your question. You will need to get in touch with the university.

That being said, it sounds like you want to transfer to a university in the US ("it's possible to be switching jobs at the end of the year with one in the US"). In that case the much larger problem will be transferring your european credits to the US institution, even if they are not expired.