6 year body retreatment

[Guest]

I see from my 2015 Forester service book that at 6 years something called a 'body retreatment' is required in order to comply with the 12 year anticorrosion warranty.

I just had the mechanical service and MOT done but the dealer didn't mention anything about retreatment.

It looks like a very expensive thing to do so I'm wondering whether any of you bothers with this, or do you just let the warranty lapse - doesn't that reduce the value of the car if not done ?

Your thoughts please