[jnellis]

Sure temperature is big factor but water is always the enemy of wood, regardless of the treatment. You can slow it down with chemicals but bugs and microorganisms find a way if water is present. Humidity is water. Primers and paint do wonders against it. But the wood has to be dry first. Tar is pretty darn good at keeping out water but also good at trapping it in.

Old growth and just 'old' wood is naturally termite resistant because wood gets harder as it ages and the bugs just don't like to chew on it, they will look elsewhere. You don't see many 60+ year old houses getting new termite infestations unless it was in areas of recent repair (fascia boards, brick moldings). But if it's wet, it's softer to chew. It's always comes down to water.