There are many reasons that liquid could vent out of jars. I doubt that I even know what all of them are, but here's a few: the jars were packed too full; the food was packed too tightly together and did not allow liquid to get in between each and every piece of food which then allowed air to remain inside the jar; if you were pressure canning, perhaps the pressure fluctuated instead of holding steady (this is one reason that ceramic-top stoves often aren't recommended for canning because of the way the burners switch themselves on and off) which can cause uneven heat/uneven pressure; if you were doing BWB canning, there might have been too little water above the jars; the liquid covering the food might never have reached the boiling point; if you were canning some kinds of starchy foods, they may have absorbed excess moisture which has the same effect as not having water covering the top of the food to the proper level in the jars; or possibly you removed the jars from the canner too quickly instead of letting them sit there the recommended time.

I have had an occasional jar spoil---I can think of two different years when it happened. With something like a jam or jelly, the telltale sign was mold in the jar. With salsa, the ring had popped off and there was visible mold. (This is one reason, though not the main reason, why it is a good idea to store canned food with the rings removed.) Other than that, I haven't encountered any with the other signs of spoilage---which could include bubbling or hissing when you open the jar, lids bulge or move instead of being firmly in place, a bad odor (not with everything but sometimes), etc. When in doubt about a jar (or a purchased can that is bulging, etc.), just throw it out. By it, I mean the food. Don gloves, dispose of the food safely in the trash (not the compost pile), and wash the container. Bleach it if doing so will make you feel better. Always be suspicious of any jar that opens too easily as if it did not have a good seal---assume the worst and don't eat it because botulism is invisible and has no odor.

I store unused jars in storage totes with lids that snap on and are held on tightly by snap lids near the handles. I stack them up in a closet in a spare room when not in use. I store used rings (after carefully removing them and hand-drying each one with a paper towel to ensure they are dry so that no corrosion occurs) in zip-lock bags, sorted by type---regular, wide, etc. and store the ziplock bags inside another storage tote. New flat lids [I buy them in bulk from Lehman's so have a huge number (sevearal hundred per pack) in storage when I get a new package of them] are stored inside a very large ziplock pack still inside their paper sleeves from Lehman's and the ziplock bag is kept in one of my kitchen cabinets so it always is handy.

Since flat lids cannot be reused safely, I save them in their own gallon-sized zip-lock bag in the pantry until I have enough to use, and then I spray paint them a nice green or terra cotta color, use a nail to hammer a hole through them, work wire through the hole, and use them as plant tags in the garden. I write on them with paint pens or garden markers. You can tie the wire to tomato cages, plant stakes, trellises, etc.

As far as a rusty or corroded lid causing a problem, I don't think they will, but if they rust or corrode and if I cannot remove the rust or corrosion with a stainless steel Scotch Bright scrubbing pad, then I remove the lid from the canning supplies. I spray paint it a bright color and use it only on jars that store something nonedible....like paper clips or magnets or crayons or whatever. I hate to throw anything away so try to find ways to reuse canning lids when they no longer are suitable for canning. You also can store packets of gardening seeds in them.

Dehydrated green beans, if dried down to the appropriately low level of moisture, ought to store in a cool, dry area in an airtight container for at least a year. You can rehydrate them by boiling them in water for 10-15 minutes and add whatever flavorings or seasonings or other ingredients you normally wood. They will be drier or chewier than green beans that never were dehydrated and I agree with George that one of the best uses for dehydrated green beans is just to add them to soups or stews.

Are you talking about dry cowpeas stored in an airtight container? They'll stay good forever, like George said. Canned ones? The quality is highest within the first year, but they can be used for several years if stored in cool, dry conditions.

I don't think I've ever put roasted tomatoes through a tomato strainer/mill/press, but i also cannot think of a reason not to do it. Well, maybe one reason. When you roast them, you are in essence cooking them. When you can them, you're pretty much cooking them again. So, I think that roasting them first and then canning them has the potential to give you an overcooked product, but I don't think that is a dealbreaker. There are some great canning recipes out there that call for the use or roasted tomatoes (and sometimes roasted garlic or other veggies) and if the roasting plus the cooking/canning was overkill, I doubt those recipes would exist.

Hope I covered everything and hope this helps.

Dawn