What is good today may be bad tommorow, although some lenses remain good for ever.

I do have sympathy for certain brands but I will never push or even strongly recommend a certain brand or product to someone when asked for advise anymore.
I have a few bad experiences with that. I was really enthousiastic about the G1 and recommended it to my stephfather, a Hasselblad and Leica user in the past, because he wanted advise from me. I said; I never advise people anymore to buy a certain product, because often they are unsathisfied with it and blame me afterwards.
He never dared to tell me he didn't use the G1 anymore because he could not handle the interface and secretly bought a Sony point and shoot. :ROTFL:
And for myself I am not brandloyal. But I do like open platforms like Android. And M4/3 and the Sony Nex (7) with which one can explore the whole lenshistory.
In my eyes it is plain silly to be fanatic about brands. Enthousiastic about certain products,yes.
I know people who have been driving Volvo's their entire lives. Fine cars, if you can afford them, but boring.
I am to fickle for this kind of loyalty.
Michiel