The OP is asking how long the case will remain exactly and precisely the same size, not how long until there is a restyling.
well, only Apple knows that until we do.
Also 100% serious question here, do people really put cases on their MacBooks?
I tried it years ago, and found the case did more scratching and denting of the edges of my computer than it did just being without one.
So outside of different styles and such, is there really that much benefit?
I mean, it’s sitting on a desk or in your lap when you’re using it, and then when you’re carrying it it’s usually in a bag or something.
Maybe it’s just me. I completely understand wanting to put a case on the slab of glass you toss around all day and is constantly in your hand.
But I don’t really understand the cases on MacBooks idea.
I even more don’t understand why anyone would put a screen protector on a MacBook, but I guess people do.