I have a pre-pandemic GUF1(extended twice) about to expire and looking for ways to retain some benefit without knowing when I will travel. E.g. I often visit my brother in Germany so am thinking I could book an Avios return in Y for some date next summer and upgrade it with the GUF1.
If I need to change an Avios booking currently, it is free as I’m GGL. Will the GUF1 upgrade survive any future changes I make (ie. Changes after the original expiry date of the GUF)?