Copteterme species of termites are the most widely spread and damaging to our assets or timbers in service. We understand their common habits as being subterrainean and using accessible moisture as an important means of survival. How ever we have encountered another well known species various times which are known to thrive in trees leaving our homes alone, "sometimes". Their habits are similar to all other subterrainean Termites and are thought to have the same needs. It's name is Nasuatermes. Without getting too technical, they are an interesting looking creature unique to all Termites! The soldier has a spike rather than two mandibules and also spits glue as the Copteterme does. What we didn't know is that they can survive being cut off from its food and moisture source for extremely long periods. So far we know they can survive 3.5 years!!! the reason we know is because the colony I am currently observing is still alive and kicking after all that time. The colony has been contained with no additional timber or water fed to them. They are probably harvesting their own fungus to feed on.
That may be the likely explanation as to why they carried on with their existence in an oregon roof beam of a home long after it was treated. If they some how become isolated and under pressure to survive and circumstance prevails then they may live to spread once again.