It you only have a few baskets then I would change the compost. I have quite a few baskets and planters so I tend to use for the second year with the addition of slow release fertiliser granules. I do however, tip the old compost out and examine for the presence of vine weevil.

I sometimes do what Jimmytheone does, other years I tip the spent compost onto the borders and let the birds have a rummage. it then gets incorporated into the soil.