What they should have done...

... before killing themselves in the cave to escape the loop....

We see them in the pool the next day -- Nov 10 -- with their memories of their previous looped existence intact. So BEFORE blowing themselves up on their last loop they should have made a huge sports bet on some event that they already know how it's going to end.

Then, on Nov 10, they go collect their fortune and spend the rest of their lives living rich.