But remember plants have different feed requirements, plants like
petunias are greedy feeders whilst heathers don't like feed, they thrive
on very poor soil.
The answer to your question is in part dictated by what you grew this
year, did you use liquid feed or additional feeding during the season.
What do you want to grow in it next year.
You could plant it up for the winter with bulbs as they have their own
food store, you could replant with winter flowering pansies as long as
you add feed or use a liquid feed over the winter.
But really it's like asking "How long is a piece of string?"

Would you say all annual bedding plants are greedy feeders? That's all I
normally grow, so it would be good to know if some of them prefer poor
soil.