I've always been a strong believer in consumer rights, which is why I always appreciated GOG's "gamers first" approach to business. Even more than Valve, GOG usually goes that extra mile to make sure you're happy with your purchase. Now they're improving their return policy, so that you can request a refund any time during the 30 days after your purchase. No matter how long you've played the game, if it's still in that 30 days, you can get a refund. This applies to early access Games in Development and individually-purchased DLC. If you pre-order a game, you can get a refund for the entire period of the pre-order and 30 days after launch.
This is why I go out of my way to do business with GOG. They haven't ripped me off yet, their products usually work on modern OS, and when it comes to issues like refunds, they usually have my back. Check out the details at their refund FAQ.
GOG’s Updated Refund Policy has your back (even more)
Everyone at GOG believes in a 'gamers-first’ approach. It means that every part of our store is designed with gamers in mind and your purchase safety and satisfaction come first for us. The latest update to our voluntary Refund Policy adds another piece to this customer-friendly experience. And it all sums up in one sentence: starting now, you can get a full refund up to 30 days after purchasing a product, even if you downloaded, launched, and played it. That's it.
It’s important for us to say that this update is possible thanks to your respect for all the time and hard work put into creating the games you buy on GOG.COM and playing by the rules. We're grateful for that and encourage you to continue to do so.
For more details on how the change works, please check this FAQ article.