I think it just flashes at random intervals to get your attention to make double sure you put the gear up and the engines aren't running at 102%. Conditions to set the caution light off are..
1) autopilot on
2) Captain sleeping
3) USA Today or magazine out
Proper required memory procedure is simple, and it always works.
1) notice shiny flashing light
2) look at captain to see if he is still alive
3) notice that he is simply sleeping as you were not fortunate enough to move up a seniority #
4) close paper or magazine, and at this point light will extinguish.

I think this it has something to do with the action of the paper closing. Later in flight should the light flash again only step 4) is needed to extinguish the light this time