Seicross is one of those games that tests your ability to play by being endless and going until you can't go any more.

But that doesn't mean that your game ever has to end.

If you go to the title screen

And on Controller 2 hold Left + A + B

while simultaneously pressing Up, Up, Down, Down, Start on Controller 1 (this part may require more hands than you have, you might consider asking for help)

When you start the game, your bike will be uncrashable!

Which means you could just go to bed and wake up the next morning to a high score and some ridiculous amount of progress

But there's no way I know of to actually end the game, short of pressing the Power or Reset buttons.