To me, there is no such thing as a ‘forever’ bike. I have a couple that aren’t worth a lot of money and have special meaning to me but I could let them go.
I also have a few ‘grail’ bikes but if someone wanted one bad enough I would let those go since it is likely they will go to someone who would also cherish them.
Eventually there is some sort of tipping point. The frame is too racey, it doesn’t fit, it’s collecting dust, the value is too significant to ignore, etc. It went from someones idea of ‘forever’ or ‘grail’ to being set free for someone else to enjoy which is how I acquired them.
My 2 cents….