But that's only assuming you are able to demo enough of them in models and sizes that work and also find that love..Not to mention finding the conditions when you demo that are on par with what your use to spending most your time skiing in. Nothing about that is technically "right away" but can actually be quite the process.
But also.....isn't it also very possible an initial love for a ski can (via some more extended ski time) end up being something you no longer feel are as great as you originally thought? and perhaps even be unhappy with? I mean you can grow to love a ski you ended up buying without demoing but imo it would then stand to reason that you can also grow to hate a ski you thought were great on a demo. We can generalize but I just don't think there is anything ensuring for certain either way.
I don't think you'll grow you hate a ski you love just because of time.
But you might grow out of that ski by becoming a more proficient skier or by changing the sort of terrain you ski on most of the time. That is unlikely to cause hate, just more of a nagging feeling it's time to move on.
I've never grown to hate a ski I liked while demoing. For that matter, I don't remember ever HATING a ski at all.