For me, it depends on where you found the email address. Broadly speaking, hotels tend to stay away from email to avoid the issue of people thinking they can make/change/cancel a room reservation.

If the email address is listed on the official website for the hotel, then you should expect a response in a reasonable amount of time. If the email was found elsewhere (like Trip Advisor), I wouldn't have the same expectations.

Also, remember that email can sometimes get marked as SPAM before any human ever sees it. Conversely, if the hotel responses by cutting/pasting part of their website, your SPAM filter might see the email as advertising.