I can't do what is described in the OP. Probably because I've seen all the episodes so many umpteen times that the endings to them all are memorized in my brain for life.
This does not detract from my enjoyment of the show, though.
I've watched the DS9 series dozens of times and always find something new and fascinating each and every time. I could never get bored of DS9 even if I've seen every episode a million times.
Mainly with the nuances the many master actors give to everything they do on the DS9 show. Talking about characters like Garak, Weyoun, Dukat, Kai Winn, Quark, Odo, and many more...their performances are fascinatingly complex and require repeating viewings in order to come to notice and appreciate all the little nuances they layer into them.
Example: Sure you know that happens with the Feds and Dominion and all the plot, but did you notice the first couple of times you watched it how Weyoun is bowing politely to, nodding his head etc. to offscreen aliens while walking with and talking to Jake during the occupation? I sure didn't come to appreciate that the first couple of times simply because I was mesmerized by their conversation itself. It was only after having known their conversation word by word, that the other nuances to what Mr. Combs was doing there started to dawn on me. And stuff like that surely wasn't written into the script itself. But when you have a master actor like Jeffrey Combs on the show, it gets into the show anyways.
This is just one example of endless amounts to be found.
IMO this does not work with the other modern Trek shows, though (excluding TOS), because nuances like this simply
don't exist in them. For
those shows, I do indeed need to have forgotten what happens to get any enjoyment out of rewatching those episodes. Otherwise, I'd rather watch paint dry than watch them again.
But not so with DS9. DS9 is one of the most rewatchable shows of all-time.
