Normally I encourage my customers to get a refund if they don't like the game, but I have a few questions:

is there a maximum amount of time where after the time customers can't refund? I know there isn't DRM so we can't know how many hours the player has played the game, but isn't there supposed something like a 7-day period where customers can't refund after this time.

 I'm writing this because I've just noticed someone refunded my game after a month, which seems suspicious. They had the game for a month and then refunded it essentially getting the game for free. (I can't reveal their details as it would violate the privacy policy). How is itch.io protecting developers from such cases of refund fraud?

Also, there are some people who downloads the game 10+ times after buying and that doesn't make sense unless they are account sharing. I would be happy if a moderator could address my questions...

Best wishes.

TL;DR:

1.  Is there a time limit where you can't refund after a set time?
2.  How is refund fraud handled?
3.  How is account sharing and multiple (mass) downloads of paid games handled?

Edit: English isn't my first language so I'm sorry for any mistakes I've made. 

Community moderators don't have access to this information, sorry. You should probably contact support. But repeated downloads could be simply from a bad connection. Happens a lot.

Piracy and fraud kind of just comes with the territory especially in the realm of digital merchandise. It's kind of just one of those things that you need to learn to accept unless you want to go down the DRM route (and even then no game is truly safe, because even the strongest DRM can be cracked). Regardless, even if someone WAS account sharing, unless they flat out admitted to it there is nothing you or the administrators can do about it as there is no limit on the amount of times a game is allowed to be downloaded in the ToS and there is no way for you to know for sure what their real reason for doing so is.  No way for you or the administrators to know whether or not someone is account sharing or if they legitimately have 10+ devices they wanted to download it to or if they just for some reason wanted to download it 10+ times or were simply having a connectivity issue and the downloads were getting corrupted or if it's just an error with the counter itself. You having a suspicion about it simply is not enough justification for you to do anything about it. I understand why you might be concerned, but the reality of the situation is that it's just something you're going to have to learn to accept if you wish to continue to make and release games.

It can take a long time for credit card fraud to be detected, as such a refund request can take a long time to get submitted if the credit card was stolen or fraudulently used.