I'll have more comments about this game later. For now, I'll just say that if you can make it past the first 6 or 7 levels, the game can be marathoned fairly easily. An extra man is awarded for every 30,000 points. Also, the bonus timer appears to have no maximum value; it keeps incrementing by 1000 at the start of each new level.
High Score: 65,746,700 (Level 176)If I can do it, anybody can.
Here's a screenshot (at the point where I voluntarily quit the game after 10-11 hours):