We use to use Rehau for our profile suppliers & they gave a 10yr guarantee with any of their upvc profile colours.
I think it is common practice to use this system in this day & age, i never knew of any other company offering more than a 10yr warranty on their products.
Plasmo is another good manufacturer but their colours are pretty standard, I would recommend the Rehau profile over any other manufacturer personally Dave.
Not sure if it really helps answer your question though
I'm not quite right you know.........