I can see that icing in the freezer is linked to air leakage past the top of
the door seal. As the seal contains a magnetic strip embedded in
plastic, I can't envisage what could possibly wear or age over time, which
makes me think it would be pointless replacing the seal; there are no moving
parts and I doubt the magnetic strip loses its effect over time.

So do these door seals lose their capacity to seal over time and, if so,
what is the mechanism of this ageing/wear process?

Thanks

Martin