"All measures that are taken to ensure a long life of wood fall under the definition wood preservation (timber treatment). Apart from structural wood preservation measures, there are a number of different (chemical) preservatives and processes (also known as timber treatment or lumber treatment) that can extend the life of wood, timber, wood structures or engineered wood. These generally increase the durability and resistance from being destroyed by insects or fungus.

As proposed by Richardson, treatment of wood has been practised for almost as long as the use of wood itself. Some accounts reach back to the beginning of recorded history. For example the Bible in Genesis, 6:13-14 “And God said unto Noah… make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch it within and without with pitch.” There are also records of wood preservation reaching back to ancient Greece during Alexander the Great’s rule, where bridge wood was soaked in olive oil. The Romans also protected their wood by brushing their ship hulls with tar. During the Industrial Revolution wood preservation became a corner stone of the wood processing industry. Inventors and scientists such as Bethell, Boucherie, Burnett and Kyan made historic developments in wood preservation, with the preservative solutions and processes.

Linseed oil
In recent years in Australia and New Zealand, Linseed has been incorporated in preservative formulations as a solvent and water repellent to 'envelope treat' timber. This involves just treating the outer 5mm of the cross-section of a timber member with preservative eg Permethrin 25:75, leaving the core untreated. While not as effective as CCA or LOSP methods, envelope treatments are significantly cheaper as they use far less preservative. Major preservative manufacturers add a blue dye to envelope treatments. There is an on-going promotional campaign in Australia for this type of treatment. Linseed oil is used to preserve Wood fences, log cabins, and wood furniture.(Such woods as Willow, Pine, oak and exc.) The function of linseed oil as a preservative is believed to be related to its action as a water repellent and drying agent rather than a direct biocidal activity. A number of European companies have developed natural-oil-only-based treatments; no synthetic preservative such as permethrin is added. Menz Holz OHT use autoclave impregnation with linseed, sunflower and rapeseed oil for 6 to 8 hours.
Wood treated with linseed oil is resistant to denting and scratches and is easily repaired, but the surface is not as hard as a modern varnish, and the wood will slowly absorb moisture if allowed to stay wet.
Boiled linseed oil is used as a paint binder or as a wood finish on its own. Heating the oil causes it to polymerize and oxidize, effectively making it thicker and shortening its drying time. Today most products labeled as "boiled linseed oil" are a combination of raw linseed oil, petroleum-based solvent and metallic dryers. The use of metallic dryers makes boiled linseed oil inedible. There are some products available that contain only heat-treated linseed oil, without exposure to oxygen. Heat treated linseed oil is thicker and dries very slowly. This grade of linseed oil is usually labeled as "polymerized" or "stand" oil, though some types may still be labeled as "boiled".
From: Wikipedia.com

Efficacy of hot wax dipping
"Robinson and French (1984) indicated that some apiarists found that hot wax dipped treatments lasted in excess of 15 years before retreatment of the material became necessary. Some beekeepers have indicated that well-treated boxes will last for more than 20 years before further treatment is required.
The extent of microcrystalline wax penetration was determined in trials conducted in Australia by Robinson and French (1986)"
From "HOT WAX DIPPING OF BEEHIVE COMPONENTS For preservation & sterilisation "
http://www.apiculture.co.za/ (Free On-line books)