You don't need to consiously count them to remember how many of them are.
Plus, while cleaning them or checking whethe they are closed, you will be like "two done, three to go" enough times to remember "five".
Not really. I think "two rooms to go", not "x windows to go". There's no point in counting or adding, so I don't bother. Also, I only clean my windows once a year, if that. There's an hilarious story about a spider family having bred on the other side of a closed window I hadn't opened all year. That must have been at least 500 spiders. It was hard to even look through the window, so I eventually bothered to clean that one early. Maybe a mistake, seeing how half of those spiders than entered into my room, but, whatever. I don't mind spiders.