Knowing how long a game lasts dramatically affects your strategy and investment. I was thinking about this in the context of the first time you play a board game with win conditions rather than a fixed number of turns, but it applies broadly across games, and now that I think of it even more broadly across how much of yourself you are willing to invest in anything based on how much future you think it has. But back to the game context.
Some games have a fixed duration, in terms of time or turns. You can watch the clock count down in a football game. In many Eurogames, the winner is whoever has the top score after X rounds; you will have exactly X rounds every game.
Some games have win conditions. Reaching those sooner can be a powerful strategy. Your first time(s) playing, you do not know how long a game typically lasts, so you play at a non-apparent disadvantage because you do not know when to pivot from building up to cashing in.
My example of the weekend was my first game of Dinosaur Island, which is fun. One player at our table had played before, and he had a runaway victory, cashing in on objectives while the rest of us were building up for the endgame. We played the “medium” length game, and it lasted four rounds. Even the winner was surprised about that. It seems safe to say we would have played differently had we realized that investments had so little time to pay off.
I have generally favored games with win conditions over fixed numbers of turns, because the number always seemed too arbitrarily game-like. The game lasts three seasons because the game lasts three seasons. But it does have the advantage of putting everyone on even footing and letting you know in advance when the endgame is coming.