In one sitting. You'd have to get good at them by playing them over and over and over again. And they were really hard so that it would take a long time to get that good.
This was intentional. Games from the 80s had a lot more technical limitations compared to today and this was a way to increase their replay value. Otherwise you'd spend $30 on a game ($93 today) and beat a game in a couple tries, and it wouldn't be worth it.