OK, I guess it is technically possible to get 200 million in 5 hours. I just played like a maniac and got over 172 million in 4 hours and 34 minutes. Another half an hour or so and I'm sure I could have made it to 200 million... if I DIDN'T GET THAT DAMN DOUBLESHOT AGAIN!
I died with $317,000 - once again proving that big money doesn't make you invincible. I died on level 331. It's after level 300 that the alien bullets and shit weapons start coming down too fast to avoid. (in NTSC mode, anyway)