Obviously, this is a Live Chess question, I would think ... seeing as you only have Live Chess games in your archive.
Some players have lag, making their first move particularly slow. It's totally up to you how long you'll wait before aborting the game, but give it a few seconds for sure. But, again, it's up to you. I usually give a player 20 to 25 seconds ... if no move by then, I'll likely press the Abort Game button.
What if you play an opening and the opponent doesn't respond with the moves right away?