Lifetime will depend entirely on that they are made of. Biodegradable bags aren't much more than flexible cardboard. Good for a year. Made with recycled plastic or fabric, they might be good for 5-8 years with good care. Clean well between seasons. You can grow any number of plants in the bag. The issue is productivity. Might limit yourself to one plant per five gallons to optimize productivity.

If you are growing indeterminate tomatoes, I'd recommend only one plant per bag. If a regular plastic container like a nursery can, the suggestion is for one that is 15-20G per plant, as these are big plants with big root systems. The other plants are quite a bit smaller even when mature, so you could do a few multiples.

Whatever container size you chose, double it.

I will 2nd the 1 tomato plant per bag suggestion by Gardengal, and from my poor past container growing experience I'd plant just a cherry tomato variety (Sungold is good). But you may have better luck than I did, my regular tomatoes developed a lot of BER. The other 3 veggies you listed I have not tried in containers, but the peppers may yield the best results?

Just an aside, if you put these bags on the ground, and have gophers in the area, they will chew through!

You can plant micro dwarf tomatoes and grow about 3 per 15 gallon container. They only get about 10 to 16 inches tall.

I am growing these currently to get winter tomatoes, taking them outside when the temperatures are above 45 degrees, and under grow lights when it is colder. They take much longer to produce in the fall due to lack of sunlight.