Pruning Tomato plants

[tankertoad]

I live in central Texas and use Earthboxes for tomatoes.  Typically, temperatures both at night and in the daytime in July, August, and maybe some of September hinder and/or stop pollination/fruit set.  Are there any suggestions about carrying over the plants into fall through the period when fruit likely won't be produced during the hottest days of summer?  I guess what I'm really asking is if I should prune the plants (Celebrity) back, and if so, how severely to prune?

I have considered replanting with an early producer like Early Girl, but tomato transplant availability in mid-summer around where I am is nonexistent as far as I know.  I haven't started my own from seed yet, but that may be the only real solution.

Thanks

[gardendoc]

We run into the heat turning off the tomato production in the summer. I pull our plants around July 4th and sow seeds for the fall crop to be planted middle of August.

Starting your own seed is a great way to those varieties you want that aren't available from the garden centers when you want them