First, I see that you're in California in Tehachapi where its warm and dry much of the year--this is both perfect weather and a perfect climate for termites. Did you know that termites exist in every state in the US EXCEPT Alaska? In fact, Alaska is the only place where termites die annually because the ground gets so cold and develops permafrost. Other than that, termites are an inescapable part of homeownership here in the US.
That having been said, the standard termite agreement in California usually provides a guarantee against reinfestation after the Vikane fumigation for up to two years. After that, termites will likely creep back in to the structure either through the ground (subterranean termites) or by flying through the air in colonies (drywood termites). This is why its so important as a homeowner to have your home checked by termite professionals periodically--not just when you plan to sell the home. Most termite inspectors recommend an annual or bi-annual inspection to keep ahead of the pesky little critters.
Since it can take up to five years after infestation for most homeowners to notice any termite pellets (droppings) around window sills and baseboards, having the home fumigated once every 9 years is just about right in terms of frequency and it doesn't seem too excessive.
As to whether or not the condition of the home and the number of fumigation treatments indicate a more serious and systemic termite problem within the home, you'll need to confer with a qualified termite and pest control inspector for assistance in helping you review the report and help you make decisions regarding this home.
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It only takes a queen and her boy friend to start another colony from one door to next. Prevention is just as important.
If the termites are/were subterranean, be sure there aren't any plumbing/water issues making the home more attractive.
Sometimes simple things are overlooked. Don't stack firewood near anything you don't want infested with wood eating insects (including fences). Damp particle board seems to very appealing to termites.
Only you can determine how much this bothers you...but know that this is very common.
The deal breaker for most people is the extent of the house damage. If it simply requires a fumigation and the structure is sound, the fumigation is all that buyers usually care about. Twice in 9 years is about average.
I think you are going to be hard pressed to find a home which doesn't need some sort of termite treatment, unless it is new or had a treatment recently.
You best resource is to discuss this further with your Termite Inspector, who will give you the low down on termites.
All the best to you.
The only time most home owners care about termites is when they're buying or selling their home, so it is uncommon for a home to be fumigated often. That being said, that alone is not a deal breaker. You need to bring in a competent termite inspector, get their report and ask them what's going on... then you'll have your answer.