Not so with hybrids. You can never be sure what their offspring will bring, so bottom line, when working with hybrid seeds every year you have to buy more.
Beans are so good for the soil because they add lots of nitrogen. My mountain garden needs compost broken down which can tie up vital nitrogen the first year it rots. So, some of the beans I plant are allowed to go to seed. When fully matured, I shell them out and replant. You can see this new seedling has sprung up in a harvested section of my garden. I had onions in there, which have been used for salads and stir frys.
My mountain garden is producing pretty well. We're getting several yellow neck squash, zucchini, onions and bush beans every week. I wish the tomatoes would get ripe, though.
When I chose the tomato plants at the garden department in Walmart, I looked for some which were not hybrid. This way, the tomatoes will reseed themselves for next spring.
If you do this also, come spring look for the tiny seedlings when they emerge. Place a stake next to them, mulch with leaves or grass clipping and you'll be surprised how hardy they are.
The butternut squash shown in this short video were planted with last falls seeds. I harvested the squash, dried the seeds, and kept them over the winter in the door of the refrigerator in a double plastic Ziploc bag. Looks like they are true to form.
When planting different varieties of squash, be sure not to intermingle them or they will cross pollinate and not give true to type produce. The flavor will suffer and the season will be lost with inferior product.