When to switch from picking pole beans green to letting them form seeds for saving?

I'm not a beginning gardener but I am a beginner with pole beans. How do you know when in the growing year to switch from picking pole beans green to letting them form seeds for saving?  I imagine a lot of people do this, but I can't find anything anywhere that addresses this.  And my understanding is that once you stop picking them all the time, they will stop producing very many new beans.  I guess the same question goes for a bush beans. I've grown them for years, but haven't saved seeds on purpose before. I know some people grow plants just for seeds, but in my small garden I typically harvest them for a while and then let them form seeds.

I used to harvest first and then switch to seed production. But poor spring conditions wiped out my scarlet runner bean seed stock, so this year I have several poles that are focused on seed  production only. (Note that I'm in a zone with a relatively short frost-free period.)

So, this year, I'm doing it in reverse. I let large beans form and fill, undisturbed by me, right from the start. Now, I can tell the plants are focusing on seed because the blooms are much reduced. At this point, I think I can harvest the small beans from the tops of the tripods without interfering with seed production.

Personally, I don't switch. One section is green beans, another is dry beans. I'm told that if I did a first harvest of green beans from all of them, I'd get a bigger dry bean crop. But I've tested that, and didn't see any difference in yields.

If, while checking on the "dry bean" section, I notice a pod that's much younger than the others on that plant, I might pick it green to nibble on. But for the most part I just let the plants do their thing.

There are some varieties that will continue pumping out new pods, even when the older pods are ripe and dry. It's the same kind of difference you see in tomatoes, between determinate and indeterminate. Unfortunately, I don't know any company that labels their beans that way, so finding the indeterminate bean varieties is a matter of trial-and-error.

Right at the beginning here, we don't have a long enough season to pick green and dry from the same plants so I pick a good section on the trellise and mark it. Nothing is picked from those beans, I also rip out any plant growing there that doesn't come up to standard.

I like to save the first and best for seed. I watch the vines, those that look healthiest, most vigorous growth, strongest yield, least disease and bugs are identified as those to be left for seed. Generally before they are even ready as green beans. Those vines are tagged and all seeds are left to mature.

If it's a dry bean type I will sort them later and save the largest and cleanest, the rest get eaten. If it's a green bean type I only harvest to eat after a good amount have matured to seed, so a little backwards from most people on that I reckon.

To me waiting till harvest has been done and saving seed form the scraps and leftovers is a bad idea.

I'm growing a variety of cut-short beans that have been grown in my family for generations.  I only had enough seed for a 4' row and honestly they didn't grow much for two months and I almost gave up on them. Then we started getting massive amounts of rain and they took off.  I harvested about 10 lbs for canning and a few messes to eat fresh.  Of course I missed a few on the first picking, so I let those go to seed.  Also I've refrained from picking for the last few weeks so I'll have an adequate supply of seed for next year.  They're still blooming, so I'll likely harvest a mess or two for eating as well.  So I guess it really depends on how many seed you need.

Some of those Appalachian heirlooms take a while to get going and then take off in the Fall.  (I think that's why some are called October Beans.). That's so cool that you have one that has been passed down in your family!

I also try to set aside a few of the best vines to go to seed and then pick the rest to keep them bearing for an extended harvest.

I just pick everything for the first half of the summer.  If a bean gets away from me and it huge, I pick it and feed it to a nearby plant.  Once the bean season is about halfway over we leave any oversize beans we miss to turn into seed.  That gives us plenty of seed for the next few years but if you're better at spotting beans than us, you may want to leave some on purpose.

Thanks everyone for your thoughts on beans for green beans and beans for seed.

It sounds like:

Best Practice--set some plants aside  just for seed
2nd best-- let them make seeds first to get better seed, then use for green beans
and
Get more green beans this way but maybe not first quality seed -- pick grren beans then save seeds
or
the Hey if it works, go for it method.

I really appreciate hearing the diversity of ideas and what works for everyone, and am always in awe of the generosity of folks with a lot of experience on this forum.