How can I tell how long games will stay in game pass?

There's no way to know until an announcement is made that they're leaving. Since they were just added they should be there for a while. They usually announce when games will be removed about a month before.

Thank you! I am new to game pass. How long do games typically stay on game pass?

That is definitely a black spot for Game Pass but it's not up to them how long games stay.

The game has been on game pass for about a year, usually that's how long a game stays on there. Now that it has been removed, it leaves space for another game. That's how it works. If you want to continue playing that game, then you have no choice but
to purchase it.

Do you mean how long do you have access to the game with Game Pass? You can play it as long as you have a Game Pass subscription and as long as the game is included in Game Pass.