Here in Oz, it's a long growing season, so our situation is similar to the one described by Janie. Disease or shorter days finish ours off in the end, but by that time, a few new plants have sprung up from some of the dropped tomatoes or out of the compost.

We don't get frost where I live, although it does get pretty cold at night in winter, so I let the feral plants do their own thing just to see what will happen. It's mid winter now, and the feral plants were doing so well at the end of May this year that I put some plastic over them for protection. One plant in particular has grown quite large and actually has fruit on it. They aren't going red though, so I think I will pick the bigger ones soon and see if they will ripen up on the window sill.

I was always told that with tomatoes you have to pinch out the laterals. That's what we call what some others called sideshoots. They spring up in the V between the main stem and a side stem. If you don't, you end up with a lot of main stems, and the plant gets big and needs a stake for each stem. But we now are able to get 'grafted tomato' seedlings. These are very robust and it's okay to have a number of main stems. They can handle it. So it's like having at least 6 plants in one. In the end I do start pinching some of them out so the plant is not spreading itself too thin. I'll take off the top shoots as well once there is a lot of fruit setting and there are signs that the plant is getting a bit straggly.

Sometimes I suspect if I did no pruning at all, they would do fine anyway. The main thing is to feed them well, keep them well mulched to stop them drying out, and here it's recommended to water them in the early morning rather than the evening, so that they don't get diseases from having their feet wet at night. It's also recommended to water them at the base rather than on the leaves for the same reason, and not to water them in the middle of a hot day. Overwatering will make the fruit split. After a period of rain, a lot of my cherry tomatoes split. I think they are more susceptible to that than the bigger tomatoes.

Having said all that, I don't know if the heritage tomatoes need more pruning than others. They wouldn't be as vigorous as the grafted tomatoes I imagine, so some pruning is probably good. Might as well remove yellowing and dead leaves at the bottom, but it's good to have plenty of foliage to shade the tomatoes from the hot sun, so don't take too much off.