Termidor SC Termiticide/Insecticide is labeled to prevent termites if they are subterranean termites. You will need to a trench but it will protect for up to 10 years.
You definitely do not have to treat all at once. A Termidor treatment can be spread out over a few weekends or whatever time frame you want to. Please read our "How To Do A Termite Treatment" article if you have not already. You are also welcome to call us with any specific treatment questions. We are here to help.