I have only found three references to this term and they are all to do with gymnastic training equipment such as exercise bicycles. If the term is in this field it is probably correct. If not, I think you are right and "life" is not necessary.

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Я бы использовал "continuous magnetization".
life permanent - этот как бы постоянное, пожизненное.
Просто permanent - постоянное.
А тут как продолжительное, я бы использовал continuous.

Remanence or remanent magnetization or residual magnetism is the magnetization left behind in a ferromagnetic material (such as iron) after an external magnetic field is removed. It is also the measure of that magnetization.
https://en.wikipedia.org/wiki/Remanence

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