yes you do need to refresh the wax. I have a little tin of wax that came with my Carradice Nelson bag and based on previous experience it will only need to be done every 2-3 years, under normal use. I have cotton duck backpacks and other bags that are approaching the 35 year old mark and still in decent shape. The cordura is a very durable product too. Other than the fact that the cotton is a renewable resource and the nylon is an oil derivative IMHO there is little difference in the durability. I have some cordura bags that originally had a water proof coating (urethane?) that has since worn off, so they are no longer water proof. I have had some luck resealing them using NikWax products. But once the waterproof coating goes it is an uphill battle.

Aaron