From what have read and actually retrieving 1 or 2 unintentionally with boat anchors would say depends on several factors; 1- how FERTILE are the waters they are going into; a cedar going into a quarry or gravel pit type enviroment will last 2- 3X longer than the same cedar going into a very fertile body of water. 2- WHICH species of cedars- am no biologist but have read some are simply more persistant than others. 3- was the cedar allowed to dry out first? Contrary to all logic, a cedar tree/ shrub that has been dried out first then sunk will outlast 1 that hasn`t. And yes the denser cedars aren`t as useful DIRECTLY as cover; BUT being denser they are more useful for fingerling bass and prey., and as spawning cover for other types of fish. Using both thick and thinner cover TOGETHER as well as say 10 hole bricks creates a variety of habitats in 1 set of attractors. And set on transition zones where bottom types change in my opinion makes them all the MORE productive.