I cheat and would rather exercise as diets are not designed to be fun.

No, diets are not fun, that's not their purpose but there's no lifestyle change without changing your eating habits.

When do the decorations come down?

That depends on the tree and the family habits. We have real pine trees, which don't last 10 years, but mid January I think is a good period to throw it out. After that, they start to lose their leaves and all you get is a big mess on the floor.