I had a fellow show up at 1 pm for my 3 pm check in. I said nicely that check in was at 3pm but I let him in because the room was pretty much ready. He deducted a star for check in as well as a couple of other categories, a 4 star overall and left a one word review: “nice.” I have 98% 5 star and over 300 reviews so his review didn’t hurt my rating but it did annoy me. I can only imagine he didn’t like being told to his face that check in was at 3 pm.
There are a few ways to prevent early check ins. Use a smart lock with a code that doesn’t work until check in time. If your check in instructions clearly say the code won’t work until check in time maybe they won’t show up until then. Don’t tell them your cleaners will be there because then they show up and bully the cleaners. I don’t have a smart lock but I’ve started delaying the sending of check in instructions until the afternoon of arrival day in hopes that will prevent people from coming early. Despite this I’ve had several guests who show up at 2 pm anyway.