If you are content with the production you have and don't want anymore then you can top them whenever you wish.

Personally I would never recommend topping any plant but would work to improve the support system instead as I prefer to get maximum production. But the choice is yours.

From one of the previous discussions on topping plants:
If I chop off the growing tips, will it produce new suckers down below? If not, or even if so, is there any way I can encourage it to grow new suckers on the lower portion of the stem?
Basically, no. That's not the nature of vining plants. New growth, new production will always be at the top end of the vine and circulation is gradually reduced and then cut off from the lower branches. Which is why topping indeterminates isn't recommended unless you don't care if you lose all that production,

Instead as most of us do, just support it to 6-7' and then let all the new growth drape back down over the support and continue to grow. The vines do fine and you get more tomatoes.

Dave

Thanks Dave. I believe I'll take your advice and just let things grow. Until now, I have used the typical wire tomato cage and experienced a lot of vine breakage once things got above the top of the cages. That was what I feared would happen as well with the new supports and why I considered topping off the plants. Based on your response, I assume this is less likely to occur with the higher supports.

As my supports are about 12 feet long and 4 feet apart, would it be of any value to add some additional horizontal support to the system to assist holding up the vines once they begin to cascade downward? I'm thinking a trellis net hung between the two supports, or possibly bamboo poles laid perpendicular to the main supports. I have access to all the bamboo I can cut down.

would it be of any value to add some additional horizontal support to the system to assist holding up the vines

Sure. You can do it by just adding more strings horizontally. Look at pics of a Florida weave. It is easy to convert stringed plants to Florida weave supports. You can also tie the tops to the horizontal bar so they run parallel to the ground.

Keep in mind for next year that the more you prune the laterals off an indeterminate the taller the central core plant will get to compensate. So leaving more lateral branches (aka suckers) and stringing them generally results in shorter plants (not short but shorter :).

Dave