I don't recommend keeping tomato plants more than one year. They tend to build up pest and disease problems and it can be a challenge to get them through the winter, requiring cold protection to do so.
Tomato plants are not too expensive and I think you will have much better results choosing recommended varieties and replanting at the recommended times each year. The following web site provides some recommended varieties for Harris County:
This next web site provides the best times of the year to plant:
Thanks for contacting your Texas A&M AgriLife Extension Office in Harris County.