https://itch.io/docs/legal/terms#refunds
The itch.io terms of service doesn't specify a time period, but for comparison, the Steam has a two-week limit and two-hour playtime cap
https://store.steampowered.com/steam_refunds
Steam also displays on reviews whether the reviewer had the game refunded, so I've had the situation where a thumbs-up review shows a refund, but at least I got the review.
Hmm, so there isn't any time limit for refunds. A week or two time cap would be reasonable though(and no reason for itch.io not to implement this policy, it would be good for devs and the platform). Only 3% of customers refunded my games anyway, so its not that big of an issue. For future projects, I'll just stick with PWYW on itch.io and release paid ones on Steam.
That's what I do, PWYW on itch and paid on Steam. A time limit sounds reasonable to me, although it hasn't reallly been an issue for me, either, it's just annoying when, for example, someone on Google Play demands a $.99 refund after playing the game for two years (one reason I'm off Google Play).
For more reference, Apple has a vague refund policy and Google has a complicated one (48hr refund window, but then they say contact the developer for a refund after that, which is problematic considering Google already took their cut).
https://support.apple.com/en-us/HT204084
https://support.google.com/googleplay/answer/2479637#policy&zippy=%2Capps-games-...
