When to save peas for seed - the first pods or later on in the plants life ?

This is my first season growing peas and as I have heritage varieties I am trying to save seed from them.

Due to my uncertainty/anxiety I have allowed several of the very first pods to mature for seeds, fearing if I did not start early I might miss the opportunity completely. I also have little awareness of the lifespan of pea plants, other than they are annuals, so had no idea how late I could risk leaving it before the plant gave up and died.

Next year, should I allow some of the first pods on the plants to mature again (those near the bottom of the plant) or should I wait until later in the season and eat the lower ones but save some from the very top of the plant for developing into viable seeds?

I have had plenty of peas for eating, but not sure if the 'maturing pods' have an effect on the cropping span of the plants even if I am picking some of the other pods around them to eat?