All the currently available games are standalone experiences, ranging from about 30 minutes to approximately 1 hour each. Since these games are already completed, I don't plan on introducing additional updates for them, at least not for now. So, if you're interested in purchasing the Winter Sale bundle, you'll have access to all the completed games. However, it would be great if you could try out free versions to see if you like all of them, but unfortunately, that's not feasible at the moment.
If you happen to have purchased the games before they are removed from sale, all your purchases - the full versions of the games you bought - will remain in your game library. This means even after they're taken off sale, all the games will remain accessible and playable for you. They'll just no longer be available for new purchases.