Valve has changed Steam's refund policy, which featured a loophole that was undoubtedly abused by at least thousands of gamers.

Steam's refund policy is quite straightforward; at its most rudimentary, a user can purchase a game and play it for up to two hours. Before the two-hour mark, the buyer was able to refund the game at zero cost, and as you can probably imagine, this loophole was easily abusable by the millions of Steam users. However, Valve has now changed its policy by partially patching up the loophole, specifically in regard to titles that are in pre-purchase and offer "Advanced Access."
For those that don't know, Advanced Access can be granted to a player that pre-purchases a title. Sometimes developers and publishers will give early access to a game to those who pre-order. The duration of this access can sometimes be as long as a week or just 24 hours. Steam's refund policy didn't count any hours played of an Advanced Access title, and only began counting after it was officially released.
As you can probably imagine, many gamers simply pre-ordered games for advanced access, played them, and then likely refunded them on the official launch day. But that strategy will no longer work, as Valve wrote in an update.
"Today we have updated a portion of our Refund Policy regarding pre-purchased titles. This change covers titles that are in pre-purchase and offer "Advanced Access". Playtime acquired during the Advanced Access period will now count towards the Steam refund period. You can find our more information regarding Steam Refunds here," wrote Valve