Leeks should be on your list of crop rotation from year to year.
There are two reasons for crop rotation when growing vegetables. One is for plant pest and disease control, and the other is for nutritional reason. The nutritional reasons for vegetable crops rotation are often overlooked.
Pest and Disease Control
Some vegetable crops will benefit from crop rotation because that are attacked - susceptible - to certain pests and diseases that live in the soil. Clubroot and eelworms are two notable cases that can live in the soil for a few years. The plants which are susceptible to attacks - Brassicas for Clubroot and onion family and potatoes for eelworm.
The main group of vegetables that need crop rotation are ...
The Legume group of vegetables normally release large quantities of Nitrogen into the soil, which is good for foliage growth. It makes sense to utilise this 'free' fertiliser the following year, by planting lettuce, cabbage and other foliage crops. this will soak up the Nitrogen.
So crop rotation for vegetables - Yes!