Around 1 hour 45 minutes to beat. This is the unedited run, aside from the first 16 minutes which I edited out. I lost my first continue 16 minutes in but accidentally chose not to continue. So I cut that part out of the video since theres no new progress. This game has unlimited continues and checkpoints so I thought it would be best to show the whole process of beating the game unedited. Even when you lose a continue you start back at whatever checkpoint you last got to. I use my discretion with each game when it comes to editing out deaths.
Check out my tutorial playthrough for 1943 for NES, which includes commentary. That was a much harder game taking around 10 hours to beat, but also has unlimited continues. Except in that game you start back at the beginning of each stage when losing a continue. 1943 is also a much better game as 1942 is very simplistic and repetitive. You can see that playthrough here