Can you tell us where you live i.e. what climate these peas are going to be grown in? That makes all the difference.

Live in Michigan. The Thumb, to be more specific. Thanks.

An inopportune heat wave can put an abrupt end to the pea crop, but I'd plan for least 20 days past first maturity date before ripping them out. Personally, here in upstate New York, I've had highly variable results how long dwarf peas will produce. Some years its just one picking and they are done, and other years they've gone on producing well into Summer.

It also depends upon variety. Most short determinate peas will ripen the majority of their pods at close to the same time. The varieties with longer vines tend to spread their harvest over a longer period... good if you want lots of peas, bad if you intend to succession plant something else in their place.

Personally, I'm not sure you could get dry seed & still have time for summer crops. I live in Wisconsin, which is probably a little harsher than your climate... but I can't get peas in early enough to plant a summer crop in their place. The DTM for the variety probably won't be accurate for a March planting. It might be better to plan a Fall garden in their place.

You are talking about summer peas(southern peas) then mine bear til frost kills them(if the deer do not get them first).
Yard beans are really running peas.
If you mean winter peas, then the Spring heat gets mine.

The remarkable amount of poor information you're getting is in part because you haven't properly stated your question, nor provided the pertinent information to get a clear response. First of all, as was stated, your zone is crucial, it determines when you plant, but also how quickly the heat comes on in summer, which is what will likely be the reason your peas stop producing. Secondly, are you growing for fresh peas, drying, or seed crop? This will determine how you manage the plot and whether you can be assured of enough time to ripen a second crop in the same plot. Whether you plant in single rows or wide beds also makes a difference - wide raised beds may dry out sooner, but thiskly planted wide beds will often maintain cooler soil temps, thus prolonging harvest. It also makes a difference in deciding which varieties to plant, assuming you are interested in optimal yield, and not conducting some agronomic experiment. The days to maturity that you are basing your calculations on is also flawed, because aside from differences in varieties, you will be planting as soon as the ground can be worked, which is not the same as optimal growing conditions. Planting a few weeks after last frost date may well give the same harvest window as you get by planting ASAP, because growing conditions (soil temp, light, water) would be more favorable. All this being said, depending on what the weather brings, your harvest could extend anywhere from 10 to 50 days... that is simply part of the nature of gardening. If you are growing for dried peas, just do a few harvests of fresh peas at first and then let the plants mature and dry as they follow their natural course. When you stop picking fresh peas, the plant will stop producing more. Once the plants stop setting fruit and have started to dry, you can remove them from the field and hang them to dry elsewhere, thus freeing your beds for subsequent plantings, but unless you undersow the peas or use transplants, you will have to calculate your second planting based on a fairly wide (and at this point unknowable) set of criteria. It is definitely not a simple question.

They can produce at least a month. Once they started getting flowers in July, they produced none stop. We had a cool Summer though. If you take care of it, and you have no heat wave, maybe they could even produce the whole summer.