The last few years I've planted seeds for late season tomatoes. This year I've taken a different strategy. First of all, it seems as if a hundred or more volunteer plants came up in my compost. So I decided to pot a few of those to use as replacements if needed. I don't care what kind of tomatoes result, after all, they will be 'home grown' and that is all that will matter for the tomatoes from those plants.
I've been pruning some of the excess sucker growth and ever occasionally snap a leader when threading it back inside the confines of the tomato cage. For many of those, the side branches are stripped, leaving only a small amount of tip growth at the end. They are then stuck in a nursery pot and placed in the shade under the potting bench. So far 100% of those have acted as though they didn't even realize that they had lost their roots. The plants just keep right on growing, and will turn into excellent plants for late season tomatoes.
I'm slowly building my inventory of these replacement plants, such that groupings will be of various ages and stages of growth. In late July or early August, I'll find a place to put them in the ground, or will replace some of the spent plants that are growing in containers. The late plants do very well in planters in late July to mid August. At that time they are fairly small plants in large containers, and don't dry out too fast. By the time the plants are much larger in late September, the temperatures have moderated therefore the plants still don't tend to have water stress issues.
Most years my late season plants make a reliable crop all the way until the first frost. Even later if I choose to cover the plants for the first light frost or two. Last year we didn't finish our tomatoes off until the second or third week in December.
For some reason, the tomatoes on old tired vines tend to become low quality in the fall, as the seed areas turn very green often with a thick consistency. Sometimes the seeds actually start to germinate in those tomatoes. On the other hand when young vigorously growing plants are started in the fall, they have always made high quality tomatoes that would rival those made during peak summer production.
IMO anyone gardening in zone 7 or below who has late season trouble with spring planted tomato plants, would be well served to start a few replacements. I've found that May and June are the best months to start the replacement plants here in zone 8, such that they have plenty of time to mature and make a crop before frost. Even gardeners in shorter season areas might benefit from having a staggered planting with a few plants planted every 3-4 weeks until mid summer. That way at any given time, one group of plants will be giving their first peak crop, and the gardener should not have periods when the tomatoes are between crops and are just coming off in a trickle.